The esp32 port moves to CMake and has S2 support, new features for rp2

This release of MicroPython adds general support in the core for using
CMake as a build system.  The rp2 port is consolidated to use the new
CMake files, and the esp32 and zephyr ports have switched to build as
pure CMake projects.  These three ports have SDKs which are built around
CMake and this change should make them easier to maintain and use.

As part of this work, CMake based ports now have support for user C
modules. Authors of user C modules should now provide both .mk and .cmake
configuration files (following the documentation and examples).

A bug was fixed in the multiple precision integer library, an arithmetic
overflow in the long division routine.  Prior to this fix certain integer
divisions would take excessive time and produce incorrect results.  See
commit 0a59938 for details.  There was
also a fix for regular expressions, to check and report byte overflow
errors when compiling expressions.  See commit
172fb52.

In the uasyncio library, a new MicroPython extension has been added,
ThreadSafeFlag, which can be set from outside the asyncio event loop,
such as other threads, IRQs or scheduler context.  It allows preemptive
code like IRQs to signal asyncio tasks, which are by nature cooperative
(non-preemptive).  asyncio.current_task() has also been added, with the
same semantics as CPython.

As mentioned above, the esp32 port has switched to a full CMake-based
project, and traditional make capability has been removed (although a
simple helper Makefile remains to keep top-level build/deploy commands
consistent with other ports).  Because of the move to CMake, network.LAN
support has been removed, to be added back in the future (use a prior
release if LAN is needed).  Basic support for Non-Volatile-Storage is added
to the esp32 module.  And there is also preliminary support for ESP32S2
SoCs and USB, with a GENERIC_S2 board defined.

On the mimxrt and samd ports, USB CDC TX handling has been fixed so that it
now works reliably.

The rp2 port has had many more core Python features enabled, along with the
enabling of ubinascii.crc32(), the uos.VfsFat and machine.Signal classes,
and the uerrno module.  uos.urandom() has been added and machine.freq() can
now change the CPU clock frequency.  The machine.UART class now has support
for timeout/timeout_char, inverted TX/RX lines, and buffered TX/RX with
configurable sized buffers.  For PIO, StateMachine has added restart(),
rx_fifo() and tx_fifo() helper functions, and support for FIFO joining.
There is now support for user C modules (via CMake) and for building
different board configurations (the default remains the PICO board).  USB
reliability has been improved.

For the stm32 port, there is now more configuration options for boards,
such as USBD VID/PID and fine-grained selection of modules.  The UART class
now supports LPUART on L0, L4, H7 and WB MCUs.  WB MCUs have a fix for a
race condition accessing the BLE ACL free buffer list, and a workaround for
a low-level BLE bug.

The zephyr port has been updated to use zephyr v2.5.0, and now builds
MicroPython as a CMake target.

What follows is a detailed list of changes, generated from the git commit
history, and organised into sections.

Main components
===============

all:
- rename BYTES_PER_WORD to MP_BYTES_PER_OBJ_WORD
- add .git-blame-ignore-revs for fixing up git blame output

py core:
- gc: don't include mpconfig.h and misc.h in gc.h
- remove BITS_PER_WORD definition
- rename BITS_PER_BYTE to MP_BITS_PER_BYTE
- rename WORD_MSBIT_HIGH to MP_OBJ_WORD_MSBIT_HIGH
- gc: change include of stdint.h to stddef.h
- mpz: fix overflow of borrow in mpn_div
- add core cmake rule files
- expand lists in core cmake custom commands
- mkrules.cmake: rename QSTR_DEFS variables to QSTRDEFS
- mkrules.cmake: add MICROPY_QSTRDEFS_PORT to qstr build process
- nlr: implement NLR for AArch64
- nlrx64: fix typo in comment
- vm: for tracing use mp_printf, and print state when thread enabled
- rename remaining object types to be of the form mp_type_xxx
- py.cmake: move qstr helper code to micropy_gather_target_properties
- py.cmake: introduce MICROPY_INC_CORE as a list with core includes
- profile: resolve name collision with STATIC unset
- runtime: make sys.modules preallocate to a configurable size

extmod:
- vfs_posix_file: allow closing an already closed file
- btstack: add HCI trace debugging option in btstack_hci_uart
- btstack: add stub functions for passkey, l2cap bindings
- btstack: enable SYNC_EVENTS, PAIRING_BONDING by default
- uasyncio: add asyncio.current_task()
- add core cmake rule files
- nimble: ensure handle is set on read error
- moduselect: fix unsigned/signed comparison for timeout!=-1
- uasyncio: add ThreadSafeFlag
- nimble/hal/hal_uart: fix HCI_TRACE format specifiers
- modbluetooth: allow NimBLE to use Zephyr static address
- modussl: fix ussl read/recv/send/write errors when non-blocking
- btstack: use MICROPY_HW_BLE_UART_BAUDRATE for first UART init
- modbluetooth: separate enabling of "client" from "central"
- extmod.cmake: add modonewire.c to MICROPY_SOURCE_EXTMOD list
- modbluetooth: free temp arrays in gatts register services
- re1.5: check and report byte overflow errors in _compilecode
- extmod.cmake: add support to build btree module with CMake

lib:
- tinyusb: update to version 0.8.0
- mbedtls: switch to currently latest commit of LTS branch v2.16
- utils/gchelper_generic: implement AArch64 support
- pico-sdk: update to latest version 1.1.0

drivers: no changes specific to this component/port

mpy-cross: no changes specific to this component/port

Support components
==================

docs:
- library/uasyncio.rst: add docs for ThreadSafeFlag
- develop/cmodules.rst: document C-modules and micropython.cmake
- develop: improve user C modules to properly describe how to build

examples:
- usercmodule: add micropython.cmake to the C and CPP examples
- usercmodules: simplify user C module enabling
- embedding: fix example so it compiles again

tests:
- extmod/vfs_posix.py: add more tests for VfsPosix class
- extmod: add test for ThreadSafeFlag
- multi_bluetooth: add basic performance tests
- rename run-tests to run-tests.py for consistency
- run-tests.py: reformat with Black
- multi_bluetooth: skip tests when BLE features are unsupported
- extmod/vfs_fat_fileio2.py: close test file at end of test
- run-tests.py: provide more info if script run via pyboard crashes
- feature_check: check for lack of pass result rather than failure
- net_inet: add 'Strict-Transport-Security' to exp file

tools:
- add filesystem action examples to pyboard.py help
- ci.sh: change esp32 CI to work with idf.py and IDF v4.0.2
- makemanifest.py: allow passing option args to include()
- ci.sh: update zephyr docker image to v0.11.13
- verifygitlog.py: show required format regexp in error message
- pydfu.py: support DFU files with elements of zero size
- ci.sh: add CI for CMake USER_C_MODULE support
- ci.sh: build user C modules for esp32
- metrics.py: fix esp32 output filename due to move to CMake
- ci.sh: build esp32 using IDF v4.0.2 and v4.3

The ports
=========

all ports:
- remove def of MP_PLAT_PRINT_STRN if it's the same as the default
- update to build with new tinyusb

bare-arm port:
- clean up the code, make it run on an F405, and add a README

cc3200 port: no changes specific to this component/port

esp8266 port:
- modules: fix fs_corrupted() to use start_sec not START_SEC

esp32 port:
- add support to build using IDF with cmake
- esp32_rmt: don't do unnecessary check for unsigned less than zero
- add explicit initialisers to silence compiler warnings
- remove traditional "make" capability
- boards: remove old IDF v3 sdkconfig values
- boards: enable BLE on all boards
- README: update based on new IDF v4 cmake build process
- add support to build with ESP-IDF v4.1.1
- add support to build with ESP-IDF v4.2
- remove obsolete IDF v3 code wrapped in MICROPY_ESP_IDF_4
- modsocket: remove unix socket error code translation
- set MICROPY_USE_INTERNAL_ERRNO=0 to use toolchain's errno.h
- boards: enable size optimisation for builds
- add support to build with ESP-IDF v4.3 pre-release
- add basic support for Non-Volatile-Storage in esp32 module
- make machine.soft_reset() work in main.py and reset_cause()
- define MICROPY_QSTRDEFS_PORT to include special qstrs
- Makefile: specify port and baud on erase_flash command
- machine_hw_spi: use default pins when making SPI if none given
- restore USER_C_MODULE support with new CMake build system
- fix multiple definition errors with mp_hal_stdout_tx functions
- enable btree module
- modsocket: correctly handle poll/read of unconnected TCP socket
- add initial support for ESP32S2 SoCs
- add support for USB with CDC ACM
- boards: add GENERIC_S2 board definition
- machine_pin: use rtc_gpio_deinit instead of gpio_reset_pin

javascript port: no changes specific to this component/port

mimxrt port:
- fix USB CDC handling so it works reliably
- boards: add MIMXRT1050_EVK board, based on MIMXRT1060_EVK
- enable CPYTHON_COMPAT, PY_ASYNC_AWAIT, PY_ATTRTUPLE options

minimal port: no changes specific to this component/port

nrf port:
- drivers/usb: add USBD_IRQHandler which calls tud_int_handler

pic16bit port: no changes specific to this component/port

powerpc port: no changes specific to this component/port

qemu-arm port: no changes specific to this component/port

rp2 port:
- machine_adc: only initialise the ADC periph if not already enabled
- micropy_rules.cmake: fix makemoduledefs vpath to work with abs path
- use local tinyusb instead of the one in pico-sdk
- enable MICROPY_PY_UBINASCII_CRC32 to get ubinascii.crc32()
- enable VfsFat class for FAT filesystem support
- machine_uart: add timeout/timeout_char to read and write
- machine_uart: add support for inverted TX and RX lines
- rp2_pio: allow more than 8 consecutive pins for PIO out/set/sideset
- rp2_pio: fix sm.get(buf) to not wait after getting last item
- modmachine: allow changing CPU clock frequency
- modmachine: re-init UART for REPL on frequency change
- rp2_flash: prevent MICROPY_HW_FLASH_STORAGE_BASE being set negative
- enable uerrno module
- enabled more core Python features
- modmachine: enable machine.Signal class
- use core-provided cmake fragments instead of custom ones
- mpthreadport.h: cast core_state to _mp_state_thread_t
- add support for USER_C_MODULES to CMake build system
- don't advertise remote wakeup for USB serial
- CMakeLists.txt: enable USB enumeration fix
- import uarray instead of array in rp2 module
- rp2_pio: validate state machine frequency in constructor
- moduos: implement uos.urandom()
- rp2_pio: add StateMachine restart,rx_fifo,tx_fifo helper functions
- machine_uart: add buffered transfer of data with rxbuf/txbuf kwargs
- add support for building different board configurations
- rp2_pio: add fifo_join support for PIO

samd port:
- mphalport: fix USB CDC tx handling to work reliably

stm32 port:
- uart: add uart_set_baudrate function
- mpbthciport: only init the uart once, then use uart_set_baudrate
- mboot: add unpack-dfu command to mboot_pack_dfu.py tool
- usb: allow a board to configure USBD_VID and all PIDs
- make pyb, uos, utime, machine and onewire modules configurable
- boards: disable onewire module on boards with small flash
- mpbthciport: fix initial baudrate to use provided value
- mpbthciport: use mp_printf instead of printf for error message
- mpbtstackport: allow chipset and secondary baudrate to be set
- mboot: after sig verify, only write firmware-head if latter valid
- uart: add support for LPUART1 on L0, L4, H7 and WB MCUs
- boards/NUCLEO_WB55: enable LPUART1 on PA2/PA3
- enable MICROPY_PY_UBINASCII_CRC32 to get ubinascii.crc32()
- rfcore: allow BLE settings to be changed by a board
- storage: prevent attempts to read/write invalid block addresses
- make-stmconst.py: allow "[]" chars when parsing source comments
- main: fix passing state.reset_mode to init_flash_fs
- powerctrl: save and restore EWUP state when configuring standby
- spi: fix baudrate calculation for H7 series
- boardctrl: add MICROPY_BOARD_STARTUP hook
- Makefile: fix C++ linker flags when toolchain has spaces in path
- Makefile: allow QSTR_DEFS,QSTR_GLOBAL_DEPENDENCIES to be extended
- include .ARM section in firmware for C++ exception handling
- powerctrl: allow a board to configure AHB and APB clock dividers
- powerctrl: support using PLLI2C on STM32F413 as USB clock source
- boards/pllvalues.py: relax PLLQ constraints on STM32F413 MCUs
- mpconfigport.h: add support for a board to specify root pointers
- boardctrl: give boards control over execution of boot.py,main.py
- boards/NUCLEO_L476RG: add 5 remaining UARTs
- rfcore: fix race condition with C2 accessing free buffer list
- rfcore: intercept addr-resolution HCI cmd to work around BLE bug
- boards: split UARTx_RTS_DE into UARTx_RTS/UARTx_DE in pin defs
- uart: use LL_USART_GetBaudRate to compute baudrate
- sdram: make MICROPY_HW_FMC_BA1,MICROPY_HW_FMC_A11 optional pins

teensy port: no changes specific to this component/port

unix port:
- mpbtstackport_common: implement mp_bluetooth_hci_active
- moduselect: don't allow both posix and non-posix configurations
- improve command line argument processing
- main: make static variable that's potentially clobbered by longjmp

windows port: no changes specific to this component/port

zephyr port:
- update to zephyr v2.5.0
- disable frozen source modules
- remove unused build files
- build MicroPython as a cmake target
- boards: add support for the nucleo_h743zi board
- modusocket: fix parameter in calls to net_context_get_XXX()

New rp2 port, BLE pairing, bonding and l2cap APIs, and docs on internals

This release of MicroPython sees the addition of a new "rp2" port for the
new Raspberry Pi RP2040 microcontroller, a dual-core Cortex-M0+ MCU with
programmable IO.  This port is built on the pico-sdk and MicroPython sits
very close to the bare metal.  The programmable IO is supported via the
@rp2.asm_pio decorator which allows writing inline assembler to be run on
the PIO state machines.

The ubluetooth module has seen significant improvements, fixes and
additions.  BLE events are now synchronous on unix and stm32 so that user
Python callbacks are called directly from the BLE stack (from NimBLE).
This helps with the new pairing and bonding API.  There is also a new l2cap
API for much faster raw data transfer between BLE devices.

Many new sections have been added to the existing "Developing and building
MicroPython" chapter to make it all about the internals of MicroPython,
including details about the MicroPython compiler, and how to port to a new
system.  This documentation work was done as part of Google's Season of
Docs 2020.

The native emitter and inline assembler now fully support ARMv6M, for
Cortex-M0+ CPUs.  There is also support added for C++ user modules on
unix, stm32 and esp32.  And reproducible builds can now be achieved by
setting SOURCE_DATE_EPOCH in the shell build environment.  Qstr
preprocessing is now done in parallel to speed up building, and there is
a new tools/ci.sh script with all functionality to run the continuous
integration tests.

The machine.I2C and machine.SPI classes have been modified so they no
longer construct both software- and hardware-based peripheral instances.
Such construction is now split to explicit soft and non-soft types by the
introduction of machine.SoftI2C and machine.SoftSPI classes.  See below for
more information.

The wait_for function in uasyncio now handles cancellation correctly,
VfsLfs supports mounting in read-only mode, and the urandom module will
randomise its seed on import on stm32, esp8266, esp32 and rp2 ports.

A new raw-paste mode is added to the REPL which includes flow control
between the device and host, as well as a mechanism where the device pulls
in data from the host as it parses the input.  This makes pasting code
faster, more reliable and use less memory.  This feature is supported on
all ports that have a raw REPL and still supports previous REPL behaviour.
See the documentation for more detail on this raw-paste mode.

The stm32 port sees improved rfcore support for WB MCUs, including flash
locking for writes when BLE is active, and a script for automatic update of
FUS/WS firmware.  New hooks are added for boards to configure the top level
behaviour of the system in stm32_main, and there is now support for
Ethernet on H7 processors.  Mboot now allows signed and encrypted firmware
updates.

Breaking changes in this release are:

- The "sys" module is renamed to "usys".  Ports that do not enable module
  weak links must replace "import sys" with "import usys as sys".
  See commit 40ad8f1

- machine.I2C and machine.SPI constructors are changed when using
  software-based I2C and SPI.  Code that constructed I2C/SPI peripherals in
  the following way will need to be changed (or else their use will emit a
  warning which will eventually be an error):

    machine.I2C(-1, ...)            ->  machine.SoftI2C(...)
    machine.I2C(scl=scl, sda=sda)   ->  machine.SoftI2C(scl=scl, sda=sda)

    machine.SPI(-1, ...)            ->  machine.SoftSPI(...)
    machine.SPI(sck=sck, mosi=mosi, miso=miso)
                        ->  machine.SoftSPI(sck=sck, mosi=mosi, miso=miso)

  Code which uses machine.I2C and machine.SPI classes to access hardware
  peripherals does not need to change.
  See commits 39d50d1 and
  98182a9

- In ubluetooth, the BLE.irq() method now has positional only arguments.
  See commit 6a6a5f9

- In ubluetooth, arguments passed to the BLE.irq() callback that were
  previously bytes objects are now memoryview objects.
  See commit 81f2162

What follows is a detailed list of changes, generated from the git commit
history, and organised into sections.

Main components
===============

all:
- rename "sys" module to "usys"
- rename absolute time-based functions to include "epoch"

py core:
- objfloat: fix handling of negative float to power of nan
- fix handling of NaN in certain pow implementations
- showbc: pass in an mp_print_t struct to all bytecode-print functions
- parse: pass in an mp_print_t to mp_parse_node_print
- dynruntime.h: add mp_import_* and mp_load/store_*
- objstr: make bytes(bytes_obj) return bytes_obj
- objarray.h: add mp_obj_memoryview_init() helper function
- makeversionhdr.py: match only git tags which look like versions
- parse: expose rule-name printing as MICROPY_DEBUG_PARSE_RULE_NAME
- objdict: add mp_const_empty_dict_obj, use it for mp_const_empty_map
- objtype: handle __dict__ attribute when type has no locals
- scope: name and use id_kind_type_t
- objexcept: compare mp_emergency_exception_buf_size signed
- use unsigned comparison of chars
- add explicit initializers for default values
- vmentrytable: ignore GCC -Woverride-init
- introduce and use MP_FALLTHROUGH macro
- makeqstrdefs.py: fix beaviour when scanning non-C preprocessed files
- makeqstrdefs.py: process C++ files as well
- mkrules.mk: add target for compiling C++ files
- makeqstrdefs.py: support preprocessing C++ files for QSTR generation
- workaround clang error when building misc.h with C++ compiler
- py.mk: support C++ code for user C modules
- mpz: do sign extension in mpz_as_bytes for negative values
- binary: fix sign extension setting wide integer on 32-bit archs
- mpprint: prevent case fall-through when assert is disabled
- mpprint: fix length calculation for strings with precision-modifier
- modmath: simplify handling of positional args to reduce code size
- mkrules.mk: remove stray vpath and unused -Itmp, add $(Q) for $(AR)
- objfun: support fun.__globals__ attribute
- asmthumb: add support for ARMv6M in native emitter
- emitnative: ensure encoding to load prelude_offset doesn't change sz
- emitinlinethumb: exclude code using #if when ARMV7M disabled
- emitnative: support binary ops on ARMv6M without use of ite instr
- qstr.h: remove QSTR_FROM_STR_STATIC macro
- gc: fix debug printing of pointer
- persistentcode: introduce MICROPY_PERSISTENT_CODE_SAVE_FILE option
- makeversionhdr: honor SOURCE_DATE_EPOCH if present

extmod:
- modbluetooth: rename logging macro to be just DEBUG_printf
- modbluetooth: refactor stack/hci/driver/port bindings
- nimble: set struct alignment correctly on 64-bit arch
- nimble: make nimble_malloc work with allocated size
- nimble: implement NimBLE mutex
- modbluetooth: implement configuration of address modes
- modbluetooth: allow using mp_hal_get_mac as a static address
- btstack: add btstack support for _IRQ_GATTS_READ_REQUEST
- btstack: detect HCI UART init failure
- nimble: add timeout for HCI sync on startup
- modussl_axtls: reduce size of code that makes exception
- modbluetooth: fix handling of optional data/uuid args
- modbluetooth: make BLE.irq() method positional only
- modbluetooth: print UUIDs correctly
- modbluetooth: implement MTU
- vfs: fix lookup of entry in root dir so it fails correctly
- modbluetooth: change module-owned bytes objects to memoryview
- modure: allow \\ in re.sub replacements
- machine_i2c: rename type to SoftI2C and add custom print method
- machine_i2c: remove "id" arg in SoftI2C constructor
- machine_spi: remove "id" arg in SoftSPI constructor
- utime_mphal: add generic utime.time_ns() function
- add explicit initializers for default values
- disable -Wmissing-field-initializers for lfs2
- introduce and use MP_FALLTHROUGH macro
- vfs_lfs: support mounting LFS filesystems in read-only mode
- modurandom: support urandom.seed() without an argument
- btstack/btstack.mk: add -Wimplicit-fallthrough=0
- nimble/nimble.mk: add -Wno-old-style-declaration
- moductypes: fix storing to (U)INT64 arrays on 32-bit archs
- machine_mem: only allow integers in machine.memX subscript
- modbluetooth: make UUID type accessible outside modbluetooth.c
- modbluetooth: combine gattc-data-available callbacks into one
- nimble: poll startup directly rather than using NimBLE sem
- modbluetooth: re-instate optional no-ringbuf modbluetooth
- nimble: make stm32 and unix NimBLE ports use synchronous events
- machine_i2c: add init protocol method for generic I2C bindings
- modbluetooth: add API for L2CAP channels
- nimble/modbluetooth_nimble: fix build when l2cap unavailable
- uasyncio: delay calling Loop.call_exception_handler by 1 loop
- uasyncio: add Task.done() method
- uasyncio: fix cancellation handling of wait_for
- nimble: fail read if the characteristic is too big
- modbluetooth: add _IRQ_CONNECTION_UPDATE event
- modbluetooth: allow setting char/desc enc/auth options
- modbluetooth: allow user-specified reason in read request IRQ
- modbluetooth: add compile-config flag to enable pairing/bonding
- modbluetooth: add _IRQ_ENCRYPTION_UPDATE event
- modbluetooth: allow configuration of pairing/bonding parameters
- modbluetooth: add gap_pair(conn_handle) func to intiate pairing
- modbluetooth: add support for bonding (key persistence)
- modbluetooth: simplify synchronous invoke_irq_handler signature
- modbluetooth: add support for passkey authentication
- nimble: generate and persist a unique IRK
- modubinascii: update code, docs for hexlify now CPython has sep
- vfs: raise OSError(ENODEV) if mounting bdev without a filesystem
- nimble: reset NimBLE BSS in mp_bluetooth_init
- nimble: don't assert on save-IRK failure
- modbluetooth: add ble.hci_cmd(ogf, ocf, req, resp) function
- vfs: check block 0 and 1 when auto-detecting littlefs
- modframebuf: change int to unsigned int in format methods args
- modonewire: use pin_od_high/pin_od_low instead of pin_write
- nimble: improve the flow control for l2cap recv path

lib:
- libm: reduce size of static two_over_pi array
- utils/mpirq: add mp_irq_init func, and clean up unused init method
- utils/pyexec: add MICROPY_BOARD hooks before/after executing code
- utils/pyexec: add stdin-reader on raw REPL with flow control
- littlefs: update littlefs2 to v2.3.0
- littlefs: guard lfs2_mlist_isopen with LFS2_NO_ASSERT
- stm32lib: update library for WB v1.10.0
- libhydrogen: add new libhydrogen submodule
- timeutils: provide simple impl of extra funcs when Epoch is 1970
- pico-sdk: add new pico-sdk submodule, for the rp2 port
- utils/pyexec: remove obsolete LCD initialization
- pico-sdk: update to latest version v1.0.1

drivers:
- memory/spiflash: add MICROPY_HW_SPIFLASH_ENABLE_CACHE option

mpy-cross:
- enable more warnings

Support components
==================

docs:
- library/ubluetooth.rst: document BLE address modes
- library/ubluetooth.rst: clarify position/kw arguments
- library/ubluetooth.rst: clarify peripheral/central vs server/client
- library/ubluetooth.rst: add docs for MTU API
- develop: add notes on prerequisite tools for building native .mpy
- reference/packages.rst: fix typo, remove duplicate "port"
- update I2C and SPI docs to add reference to SoftI2C and SoftSPI
- library/btree.rst: correct method typo: __detitem__ to __delitem__
- library/machine.rst: correct minor typo: timout to timeout
- library/machine.Signal.rst: correct typo: usecases to use cases
- library/machine.Timer.rst: add mention of constructor arguments
- reference/glossary.rst: fix minor grammar error, An -> A
- fix reference to QSTR_GEN_CFLAGS Makefile flag
- develop/cmodules.rst: add link to source code for user C example
- library/ubluetooth.rst: add docs for L2CAP channels
- reference/repl.rst: add information about new raw-paste mode
- library/ubluetooth.rst: add _IRQ_CONNECTION_UDPATE docs
- library/ubluetooth.rst: update char/desc flags
- library/ubluetooth.rst: update read request IRQ docs
- library/ubluetooth.rst: add pairing/bonding config docs
- library/ubluetooth.rst: add gap_pair() docs
- library/ubluetooth.rst: add bonding docs
- library/ubluetooth.rst: add passkey docs
- develop: add MicroPython Internals chapter
- fix minor typos in RTC docs, and->an
- esp8266/quickref: add warning block about NeoPixel timing
- develop/natmod: fix a small typo, con->can
- update copyright year range to include 2021

examples:
- bluetooth: update to use positional-only args to irq()
- add example code for user C modules, both C and C++
- bluetooth: add bonding/passkey demo
- rp2: add pio_uart_rx.py example

tests:
- multi_bluetooth: update to new config('mac') behaviour
- multi_bluetooth: make ble_gap_connect robust against event timing
- multi_bluetooth: update UUID format in .exp files
- run-multitests.py: show test/truth diff
- multi_bluetooth/ble_mtu.py: add multitest for BLE MTU
- basics: enable == and != special-method tests now that they work
- basics: add test for MICROPY_PY_ALL_INPLACE_SPECIAL_METHODS ops
- run-tests: use -BS flags when running CPython
- thread/stress_schedule.py: assign globals before running test
- micropython/extreme_exc.py: unlink alloc'd lists earlier in chain
- run-multitests.py: fix diff order, show changes relative to truth
- multi_bluetooth: improve reliability of event waiting
- run-multitests.py: add a -p flag to run permutations of instances
- multi_bluetooth: change dict index-and-del to pop, to clear event
- multi_bluetooth: add a test for WB55 concurrent flash access
- multi_bluetooth: add L2CAP channels multi-test
- extmod: add vfs_posix.py test for uos.VfsPosix class
- run-tests: update skipped tests on CI for GitHub Actions
- multi_bluetooth: add multitests for BLE pairing and bonding
- misc/sys_settrace_features.py: ignore CPython zipimport traces
- extmod: add test to try and mount a block device directly
- misc/sys_settrace: make test output independent of invoked path
- misc/sys_settrace_features.py: fix running with non-dflt encoding
- extmod: add test for the precision of utime functions
- move native for test from pybnative to micropython
- extmod/utime_time_ns.py: relax bounds on time_ns measurement
- run-tests: change default Python command used on Windows

tools:
- mpy-tool.py: fix merge of multiple mpy files to POP_TOP correctly
- write msvc-compatible frozen content
- upip.py: support explicit port number in host
- makeqstrdefs.py: run qstr preprocessing in parallel
- ci.sh: add helper script to run CI tasks
- pyboard.py: add fast raw-paste mode
- ci.sh: put echo of CI path in a separate function
- ci.sh: use pip-install to get latest version of esptool.py
- ci.sh: pip install pyhy for stm32 builds
- ci.sh: for code size build, fetch history of master branch only
- ci.sh: for ci_code_size_setup, update apt to install gcc-multilib
- mpy-tool.py: list frozen modules in MICROPY_FROZEN_LIST_ITEM
- verifygitlog.py: add script for verifying commit message format
- makemanifest.py: add check that freeze path is a directory
- remove obsolete upip bootstrap script

CI:
- install setuptools for black code formatting
- update zephyr build to v2.4.0
- stop using Travis for CI
- workflows: add workflows for all CI tasks, builds and tests
- workflows: run unix and qemu-arm workflows when tests change
- workflows: fix code-size CI workflow
- workflows: add CI workflow for rp2 port
- workflows: add workflow to verify commit message format
- workflows/ports_unix.yml: add job for a reproducible build

The ports
=========

all ports:
- add utime.gmtime() function
- add SoftI2C and SoftSPI to machine module where appropriate
- support legacy soft I2C/SPI construction via id=-1 arg
- use correct in/out endpoint size in TUD_CDC_DESCRIPTOR

cc3200 port:
- ftp: add quotes to PWD response and allow FEAT prior to login
- fix debug build

esp8266 port:
- remove release-specific manifest, disable osdebug by default
- mpconfigport.h: seed the urandom module on import
- remove "FAT" from warning message in inisetup.py
- modules/neopixel.py: add timing param to NeoPixel constructor

esp32 port:
- pin MicroPython and NimBLE tasks to core 0
- mpconfigport.h: remove duplicate uhashlib registration
- boards/sdkconfig.base: set default IDF log level to ERROR
- modnetwork: re-enable PPP support for IDF-SDK >=v4
- use path relative to root for netutils/timeutils headers
- mpconfigport.h: enable MICROPY_PY_DELATTR_SETATTR
- mpconfigport.h: seed the urandom module on import
- support building C++ code
- machine_pin: reset pin if init sets mode
- remove "FAT" from warning message in inisetup.py
- modnetwork: synchronize WiFi AUTH_xxx constants with IDF values

javascript port: no changes specific to this component/port

mimxrt port:
- boards: add MIMXRT1064_EVK board

minimal port: no changes specific to this component/port

nrf port:
- main: make mp_builtin_open signature match that in py/builtin.h
- remove unnecessary includes of mpconfigport.h and its header guard
- README: describe Pin numbering scheme for nRF52840
- boards: update memory.ld to include bootloader offsets
- Makefile: add bootloader specific section
- Makefile: add support for flashing with nrfutil
- boards: add linker script for nrf52840 Open Bootloader 1.2.0
- change selected boards to utilize pre-flashed bootloader
- README: add use of "make submodules" in alternative build paragraph

pic16bit port: no changes specific to this component/port

powerpc port: no changes specific to this component/port

qemu-arm port: no changes specific to this component/port

rp2 port:
- add new port to Raspberry Pi RP2 microcontroller
- machine_pin: change N_GPIOS to NUM_BANK0_GPIOS for pico-sdk compat
- memmap_mp.ld: update for latest SDK
- rp2_pio: add JMP PIN support for PIO
- modmachine: implement additional functions incl unique_id and idle

samd port: no changes specific to this component/port

stm32 port:
- mpconfigport.h: enable MICROPY_PY_REVERSE_SPECIAL_METHODS
- uart: allow static IRQ handler registration
- modbluetooth_hci: use a static mp_irq_obj_t for BT HCI UART IRQ
- mpbthciport: increase char timeout of BT HCI UART
- make-stmconst.py: add support for WB55 header files
- rfcore: update rfcore.c to match how ST examples work
- boards/USBDONGLE_WB55: add USE_MBOOT support
- powerctrlboot: acquire HSEM5 on STM32WB during SystemClock_Config
- rfcore: fix length matching in HCI parser
- rfcore: refactor some helper funcs, and remove some magic numbers
- rfcore: enable RX IRQ on BLE IPCC channel for better performance
- boards/NUCLEO_WB55: add Python helper code for rfcore
- usb: don't nul pyb_hid_report_desc if MICROPY_HW_USB_HID disabled
- rtc.h: include py/obj.h to make header self contained
- servo: fix angle and speed methods to work again with -ve args
- led: support PWM output without TIM3
- rfcore: fix FUS layout and size of ipcc_device_info_table_t
- Makefile: allow boards to extend SRC_C, SRC_O and OBJ variables
- sdio: don't change any DMA2 settings on H7 MCUs
- sdcard: fix H7 build when using SDMMC2
- rfcore: add Python API for basic rfcore operations
- boards/NUCLEO_WB55: add standalone WB55 FUS/WS firmware updater
- rfcore: update to support WS=1.9.0.0.4
- boards/NUCLEO_WB55/rfcore_firmware.py: fix flash unlock
- boards/NUCLEO_WB55/rfcore_firmware.py: fix bad variable name
- boards/NUCLEO_WB55/rfcore_firmware.py: increase GET_STATE timeout
- fix broken build when FAT FS multi-partition is disabled
- usbd_cdc_interface: check and handle CDC TX wrap-overflow
- machine_adc: fix ADC auto-calibration to run when ADC not enabled
- mpconfigport.h: seed the urandom module on import
- rng: use SysTick+RTC+unique-id to seed pRNG for MCUs without RNG
- boards: factor out common data/bss/heap/stack linker sections
- support C++ code and user C modules written in C++
- main: move update_reset_mode to outside the soft-reset loop
- add MICROPY_BOARD calls in various places in stm32_main
- boardctrl: define MICROPY_BOARD_EARLY_INIT alongside others
- Makefile: make the generation of `firmware.bin` explicit
- Makefile: allow boards to extend all SRC variables
- rtc: validate the RTC prescaler on boot and change if incorrect
- rfcore: make RX IRQ schedule the NimBLE handler
- flash: implement WB55 flash locking
- rfcore: don't send HCI ACL cmds while another is pending
- rfcore: depend on NimBLE only when BLE enabled
- modmachine: add device and revision ids to machine.info()
- Makefile: disable text compression in debug builds
- powerctrl: define RCC_SR_SFTRSTF flag for H747
- powerctrl: fix STOP mode voltage scaling on H7 REV V devices
- powerctrl: on H7, re-enable disabled OSCs/PLLs on exit from STOP
- powerctrl: disable RTC write protection before changing flags
- powerctrl: set H7 RTC wakeup flags
- powerctrl: ensure SysTick is disabled on STOP mode entry for H7
- i2c: factor I2C finding code to i2c_find_peripheral function
- add support for a board to reserve certain peripherals
- Makefile: change -O0 to -Og for DEBUG=1 builds
- boards/stm32h743.ld: enable D2 RAM and add eth-buffer section
- eth: add support for H7 processors
- boards/NUCLEO_H743ZI: enable ethernet peripheral
- mboot: enable LFS2_READONLY for mboot builds with littlefs
- usb: allocate 128 bytes to CDC data out EPs on non-multi-OTG MCUs
- pyb_can: add ability to calculate CAN bit timing from baudrate
- system_stm32: enable DBGMCU in low-power modes for debug builds
- sdram: add SDRAM enter/leave self-refresh mode functions
- adc: deselect VBAT after reading to prevent battery drain
- main: do extended readblocks call when auto-detecting littlefs
- boards/PYBD_SF2: disable SPIFLASH_ENABLE_CACHE for mboot builds
- mboot/gzstream: fix lost data decompressing final part of file
- mboot: add support for signed and encrypted firmware updates
- boards/NUCLEO_WB55: enable MBOOT with packing mode
- Makefile: use MBOOT_PACK_KEYS_FILE as depedency of .pack.dfu
- main: check block 0 and 1 when auto-detecting littlefs
- mboot: don't auto-detect littlefs block size
- mboot: add ELEM_TYPE_STATUS element so application can get status
- mboot: introduce MBOOT_ERRNO_xxx constants and use them
- mboot/fwupdate.py: refactor update_mpy with support for STATUS
- main: introduce MICROPY_HW_FLASH_MOUNT_AT_BOOT config option
- rfcore: fix flow control for IPCC RX IRQ
- fix minor typos in RTC docs, and->an
- usbd_cdc_interface: don't wait in usbd_cdc_tx_always if suspended
- mboot: change debug compiler optimisation from -O0 to -Og

teensy port:
- fix build errors and warnings and enable -Werror

unix port:
- Makefile: always enable -f*-sections regardless of DEBUG setting
- implement BLE H4 HCI UART for btstack/nimble
- implement mp_hal_time_ns using gettimeofday
- variants: enable MICROPY_DEBUG_PARSE_RULE_NAME on coverage build
- mpconfigport.h: enable MICROPY_PY_DELATTR_SETATTR
- enable more warnings
- support building C++ code
- Makefile: move coverage.c and coveragecpp.cpp to coverage variant
- handle pending events/scheduler in MICROPY_EVENT_POLL_HOOK
- make mp_hal_delay_ms run MICROPY_EVENT_POLL_HOOK
- modtime: fix time() precision on unix ports with non-double floats

windows port:
- msvc: support freezing modules
- Makefile: support freezing modules
- show test failures in the Appveyor builds
- update build instructions in README
- implement mp_hal_time_ns using gettimeofday
- msvc: use same default python command as core

zephyr port:
- replace zephyr integer types with C99 types
- const-ify struct device instance pointers
- update build instructions to v2.4.0
- replace broken shell_net_iface() with more general shell_exec()
- guard I2C code with appropriate ifdef config
- add basic UART functionality to machine module
- machine_uart: fix arg of machine_uart_ioctl to make it uintptr_t

New uasyncio module, code formatting, BTstack bindings with unix support

This release of MicroPython includes a new implementation of the uasyncio
module which aims to be more compatible with CPython's asyncio module.  The
main change is to use a Task object for each coroutine, allowing more
flexibility to queue tasks in various places, eg the main run loop, tasks
waiting on events, locks or other tasks.  It no longer requires
pre-allocating a fixed queue size for the main run loop.  A pairing heap is
used to queue Tasks, and the core is optionally implemented in C.

Most code in this repository is now auto-formatted using uncrustify for C
code and Black for Python code.  The tools/codeformat.py script is used to
apply this formatting.  Options for uncrustify were chosen to match as
closely as possible the existing C style, but there were nevertheless quite
a few changes to make the code style consistent.

BlueKitchen BTstack bindings have been added for the ubluetooth module, as
an optional alternative to the NimBLE stack.  The unix port can now be
built with BLE support using these bindings, which works with USB Bluetooth
adaptors (this feature is enabled by default on the dev and coverage
variants).

Other Bluetooth additions include: new events for service/characteristic/
descriptor discovery complete; new events for read done and indicate
acknowledgement; and support for active scanning in BLE.gap_scan().  See
also below for breaking changes to the ubluetooth BLE API.

PEP 526 has been implemented which adds new syntax for variable
annotations, such as "x:int = 1".  PEP 572 has also been implemented, which
adds the ":=" operator for assignment expressions, such as "if x := 1:...".

The whole code base now supports compressing error messages (those strings
used as arguments to exception instances) using a "common word" scheme,
which can be used to reduce code size.

Other new features include: support for non-boolean results for equality
and inequality tests; the addition of the micropython.heap_locked()
function to test the state of the heap; binary operations for viper uint
operands in the native emitter; and mtime support on littlefs v2
filesystems (which can be disabled if needed).

There has been an important bug fix when importing ARM machine code from
an .mpy file: the system now correctly tracks the executable memory
allocated to the machine code so this memory is not reclaimed by the
garbage collector.

For testing, a multi-instance test runner has been added (see
tests/run-multitests.py) which allows running a synchronised test across
two or more MicroPython targets.  This is currently used for network and
BLE tests that require communication between multiple devices.

In the unix port different builds are now organised into build variants,
analogous to boards on bare-metal.  And PEP 475 has been implemented which
retries syscalls failing with EINTR.

The stm32 port sees improved support for STM32WB MCUs, with ADC, SPI and
DMA support, along with support in mboot for these MCUs.  Mboot also adds
optional littlefs support.

The esp8266 port now includes three generic board definitions:
GENERIC_512K, GENERIC_1M and GENERIC, with the latter for modules with 2M
or more of flash.  This port also changed the default filesystem to
littlefs, and no longer supports hard pin IRQs.  See breaking changes below
for more details.

The esp32 port now enables Bluetooth support (via NimBLE) on both IDF v3
and v4 builds.  It also changes the default filesystem from FAT to littlefs
v2 (but existing devices with FAT filesystems will continue to work without
change).

There is also a new mimxrt port which targets NXP i.MX RT series CPUs.

Breaking changes in this release are:

- async-for no longer await's on the result of __aiter__.  The __aiter__
  method should return an async-iterable object but is not itself
  awaitable.
  See commit 37e1b5c

- In ubluetooth, the IRQ event constants have all changed value (from a
  bitfield to a sequential integer) and Python code should be updated
  accordingly by replacing the const definitions with the new ones, which
  can be found at
  https://docs.micropython.org/en/latest/library/ubluetooth.html#ubluetooth.BLE.irq
  See also commit e6881f0

- In ubluetooth, the IRQ data for the _IRQ_SCAN_RESULT event has had the
  "connectable" entry changed to "adv_type".  The existing connectable
  value was a boolean and True now becomes 0x00, False becomes 0x02.
  See commit dd0bc26

- For esp8266, the default filesystem has changed from FAT to littlefs v2.
  And the flash layout of the firmware and filesystem has changed to give
  more space to the firmware and frozen bytecode.  When upgrading an
  existing esp8266 device the filesystem will be reformatted so files
  should be backed up first.
  See commit e0905e8

- For esp8266, machine.Pin no longer supports configuring a pin IRQ with
  "hard=True" (because the interrupt handling code is moved to iRAM).
  Existing code using pin IRQs should remove any "hard=True" argument.
  See commit 0bd58a5

- For the unix port, binaries are renamed to micropython-variant (no longer
  micropython_variant).
  See commit 977b532

What follows is a detailed list of changes, generated from the git commit
history, and organised into sections.

Main components
===============

all:
- reformat C and Python source code with tools/codeformat.py
- convert exceptions to use mp_raise_XXX helpers in remaining places
- remove spaces between nested paren and inside function arg paren
- remove spaces inside and around parenthesis
- fix implicit casts of float/double, and signed comparison
- use MP_ERROR_TEXT for all error messages
- clean up error strings to use lowercase and change cannot to can't
- fix implicit floating point promotion
- fix implicit conversion from double to float
- fix implicit floating point to integer conversions
- enable extra conversion warnings where applicable
- remove commented-out include statements
- format code to add space after C++-style comment start
- factor gchelper code to one place and use it for unix & ARM ports
- fix auto-enable of MICROPY_GCREGS_SETJMP to select GC behaviour
- update Python code to conform to latest black formatting

py core:
- remove commented-out debug printf's from emitbc and objlist
- obj.h: remove comments about additional mp_buffer_info_t entries
- objobject: add object.__setattr__ function
- objobject: add object.__delattr__ function
- nlrx86: silence possible warnings about unused nlr argument
- asmx86: fix stack to be 16-byte aligned for entry and sub-call
- asmx86: remove unused 5th argument facility
- runtime: don't allocate iter buf for user-defined types
- objsingleton: use mp_generic_unary_op for singleton objects
- introduce MP_ROM_NONE macro for ROM to refer to None object
- introduce MP_ROM_FALSE/MP_ROM_TRUE for ROM to refer to bool objects
- objstr: don't use inline GET_STR_DATA_LEN for object-repr D
- obj.h: use 32-bit shift in MP_OBJ_NEW_QSTR calc for obj-repr D
- clean up commented-out code and comments about exception hierarchy
- objslice: add support for indices() method on slice objects
- objslice: inline fetching of slice paramters in str_subscr()
- make mp_obj_get_type() return a const ptr to mp_obj_type_t
- mkenv.mk: move usage of 32-bit flags to py.mk
- unicode: add unichar_isalnum()
- runtime: move MICROPY_PORT_INIT_FUNC near the end of mp_init()
- nativeglue: use mp_const_X instead of &mp_const_X_obj
- obj.h: redefine qstr object encoding to add immediate obj encoding
- obj: add MICROPY_OBJ_IMMEDIATE_OBJS option to reduce code size
- obj: optimise mp_obj_get_type for immediate objs with repr A and C
- mpconfig.h: define BITS_PER_BYTE only if not already defined
- objint: add mp_obj_int_get_uint_checked() helper
- pairheap: add generic implementation of pairing heap data structure
- gc: don't include or init gc_mutex when GIL is enabled
- qstr: don't include or init qstr_mutex when GIL is enabled
- objgenerator: use mp_obj_new_exception_arg1 to make StopIteration
- objexcept: optimise mp_obj_new_exception[_arg1/_args] functions
- obj.h: add and use mp_obj_is_bool() helper
- release GIL during syscalls in reader and writer code
- emitnative: use NULL for pending exception (not None)
- emitnative: stop after finding an unwind target
- mpthread.h: use strong type for mp_thread_set_state() argument
- objtype: make mp_obj_type_t.flags constants public, moved to obj.h
- support non-boolean results for equality and inequality tests
- compile: allow 'return' outside function in minimal builds
- scheduler: add "raise_exc" argument to mp_handle_pending
- scheduler: move mp_keyboard_interrupt from lib/utils to py core
- scheduler: allow a port to specify attrs for mp_keyboard_interrupt
- scheduler: move clearing of kbd traceback to mp_keyboard_interrupt
- expand type equality flags to 3 separate ones, fix bool/namedtuple
- add mp_raise_type helper macro and use it where appropriate
- add mp_raise_msg_varg helper and use it where appropriate
- factor out definition of mp_float_union_t to one location
- objexcept: rename mp_obj_new_exception_msg_varg2 to ..._vlist
- objtuple: remove code that handles tuple-subclass equality test
- objtype: allow mp_instance_cast_to_native_base to take native obj
- dynruntime.h: add implementation of mp_obj_cast_to_native_base
- objarray: turn on MP_TYPE_FLAG_EQ_CHECKS_OTHER_TYPE for memoryview
- removing dangling "else" to improve code format consistency
- bc0.h: shift comment to start of line to improve format consistency
- builtinimport: adjust if-block order in find_file to clean up #if's
- malloc: put { on separate line for funcs that have selective sigs
- un-nest configuration #if/#endif's for selection of complex code
- parse: add parenthesis around calculated bit-width in struct
- builtinevex: support passing in a bytearray/buffer to eval/exec
- objstr: remove duplicate % in error string
- objstringio: expose tell() on StringIO and BytesIO objects
- modmicropython: add heap_locked function to test state of heap
- stream.h: include sys/types.h to get size_t and off_t for POSIX API
- mpconfig.h: enable MICROPY_MODULE_GETATTR by default
- pairheap: properly unlink node on pop and delete
- pairheap: add helper function to initialise a new node
- use preprocessor to detect error reporting level (terse/detailed)
- dynruntime.mk: set MICROPY_ENABLE_DYNRUNTIME instead of per module
- implement "common word" compression scheme for error messages
- objexcept: allow compression of exception message text
- parse: remove unnecessary check in const folding for ** operator
- objexcept: remove optional TimeoutError exception
- scheduler: fix race in checking scheduler pending state
- scheduler: add assert that scheduler is locked when unlocking
- makecompresseddata.py: don't prefix str with mark if not compressed
- scope: add assert to check that low numbered qstrs do fit in uint8_t
- always give noop defines when MICROPY_ROM_TEXT_COMPRESSION disabled
- objarray: fix sign mismatch in comparison
- objint: do not use fpclassify
- makecompresseddata.py: make compression deterministic
- objdict: fix popitem for ordered dicts
- stream: remove mp_stream_errno and use system errno instead
- modio: allow uio.IOBase streams to return errno for read/write error
- scheduler: add option to wrap mp_sched_schedule in arbitrary attr
- parse: support constant folding of power operator for integers
- scheduler: convert mp_sched_full and mp_sched_num_pending to macros
- parse: make mp_parse_node_extract_list return size_t instead of int
- nativeglue.h: rename "setjmp" entry to "setjmp_" to avoid any clash
- py.mk: use additional CFLAGS to compile string0.c
- modmath: work around msvc float bugs in atan2, fmod and modf
- ringbuf: fix compilation with msvc
- modsys: use consistent naming pattern for module-level const objects
- modbuiltins: fix getattr to work with class raising AttributeError
- dynruntime.h: make mp_obj_str_get_str raise if arg not a str/bytes
- objtype: add __dict__ attribute for class objects
- objtype: use mp_obj_dict_copy() for creating obj.__dict__ attribute
- obj.h: clarify comments about mp_map_t is_fixed and is_ordered
- compile: convert scope test to SCOPE_IS_COMP_LIKE macro
- compile: implement PEP 572, assignment expressions with := operator
- grammar.h: consolidate duplicate sub-rules for :test and =test
- compile: implement PEP 526, syntax for variable annotations
- misc.h: add missing semi-colon in mp_float_union_t for big-endian
- obj.h: add public mp_obj_is_dict_or_ordereddict() helper macro
- objtype: support passing in an OrderedDict to type() as the locals
- asm: add funcs/macros to emit machine code for logical-shift-right
- asm: add condition codes for signed comparisons
- emitnative: implement binary operations for viper uint operands
- objcomplex: add mp_obj_get_complex_maybe for use in complex bin-op
- obj.h: make existing MP_TYPE_FLAG_xxx macros sequential
- rework mp_convert_member_lookup to properly handle built-ins
- obj.h: fix mp_seq_replace_slice_no_grow to use memmove not memcpy
- compile: don't await __aiter__ special method in async-for
- persistentcode: maintain root ptr list of imported native .mpy code
- runtime: fix builtin compile() in "single" mode so it prints exprs
- mphal.h: introduce mp_hal_time_ns and implement on various ports

extmod:
- uzlib: explicitly cast ptr-diff-expr to unsigned
- fix modbluetooth and modwebrepl to build in nanbox mode
- modbluetooth: fix func prototype, empty args should be (void)
- vfs_posix: release GIL during system calls
- modbluetooth: implement config getter for BLE rxbuf size
- modbluetooth.h: fix typo in comment about registering services
- modbluetooth_nimble: fix wrong offset used for descriptor flags
- modframebuf: allow blit source to be a subclass of FrameBuffer
- modbluetooth_nimble: move nimble specific code, factor nimble.mk
- modbluetooth: extract out gatts_db functionality from nimble
- btstack: add empty modbluetooth implementation
- btstack: implement advertising
- btstack: implement service registration
- btstack: implement gatts_db for btstack
- btstack: implement scan and gatt client, connect and disconnect
- btstack: implement notifications/indications for GATT clients
- nimble: clarify active state and check for active in all methods
- modbluetooth: unify error handling in remaining places
- modbluetooth: change scan result's "connectable" to "adv_type"
- nimble: when getting BLE MAC try public address if random fails
- vfs: factor out vfs mount-and-chdir helper from stm32
- modlwip: fix polling of UDP socket so it doesn't return HUP
- modlwip: properly handle non-blocking and timeout on UDP recv
- vfs_posix_file: lock GIL when writing and allow stdio flush
- vfs_posix_file: include unistd.h to get STD{IN,OUT,ERR}_FILENO
- uasyncio: add new implementation of uasyncio module
- uasyncio: add optional implementation of core uasyncio in C
- uasyncio: add manifest.py for freezing uasyncio Py files
- uasyncio: don't create a Loop instance in get_event_loop()
- uasyncio: implement Loop.stop() to stop the event loop
- uasyncio: add error message to Lock.release's RuntimeError
- uasyncio: add StreamReader/StreamWriter as aliases of Stream cls
- uasyncio: add global exception handling methods
- modubinascii: make code private and module self-contained
- btstack: pass through SCAN_RSP events
- modbluetooth: provide FLAG_WRITE_NO_RESPONSE for characteristics
- uasyncio: add Loop.new_event_loop method
- uasyncio: change cannot to can't in error message, and test exp
- nimble: update to work with NimBLE 1.3
- modbluetooth: don't hold atomic section during mp_sched_schedule
- btstack: implement more robust init/deinit sequencing
- modbluetooth: fix sign compare and unused variable warnings
- modbtree: retain reference to underlying stream so it's not GC'd
- vfs_lfsx: fix path handling in uos.stat() to consider cur dir
- vfs_lfsx: normalize path name in chdir
- vfs_lfsx: fix rename to respect cur dir for new path
- modbluetooth: add support for changing the GAP device name
- nimble: make error code mapping default to MP_EIO
- vfs_lfsx: fix import_stat so it takes into account current dir
- vfs: retain previous working directory if chdir fails
- modbluetooth: make modbluetooth event not a bitfield
- modbluetooth: add discover complete events for svc/char/desc
- modbluetooth: allow discovery of svc/char by uuid
- modbluetooth: implement read done event
- modbluetooth: ensure status=0 always on success
- modbluetooth: support bigger characteristic values
- ure: use single function for match/search/sub
- uasyncio: add asyncio.wait_for_ms function
- modbluetooth: register default GATT service and fix esp32 init
- moductypes: use mp_obj_is_dict_or_ordereddict to simplify code
- vfs_lfs: fix littlefs bindings to build in nan-box mode
- nimble: fix attr NULL ptr dereference in ble_gatt_attr_read_cb
- btstack: schedule notify/indicate/write ops for bg completion
- modbluetooth: ignore unused self_in in ble_gatts_indicate
- modbluetooth: fix so it builds in peripheral-only mode
- modbluetooth: add event for "indicate acknowledgement"
- modussl: improve exception error messages
- modussl_mbedtls: integrate shorter error strings
- uasyncio: add StreamReader.readexactly(n) method
- vfs_reader: fix mp_reader_new_file to open file in "rb" mode
- uasyncio: truncate negative sleeps to 0
- vfs_lfs: add mtime support to littlefs files
- btstack: implement GAP scan duration_ms parameter
- modbluetooth: fix race between READ_REQUEST and other IRQs
- bluetooth: support active scanning in BLE.gap_scan()
- machine_i2c: fix buffer overrun if 'addrsize' is bigger than 32
- modlwip: fix error return for TCP recv when not connected
- vfs: support larger integer range in VFS stat time fields
- vfs: add option to use 1970 as Epoch

lib:
- utils/pyexec: introduce MICROPY_REPL_INFO, wrap debug prints in it
- mp-readline: add an assert() to catch buffer overflows
- mp-readline: add word-based move/delete EMACS key sequences
- utils: change default value of pyexec_mode_kind to 0 to put in bss
- utils/pyexec: handle pending exceptions after disabling kbd intrs
- add BlueKitchen BTstack submodule
- tinyusb: update to a6b916ba for i.MX support
- btstack: update to latest master btstack commit
- littlefs: update littlefs2 to v2.2.0
- mynewt-nimble: update submodule to NimBLE release 1.3.0
- btstack: update to c8b9823 for USB HCI reset timeout fix
- nrfx: upgrade to nrfx v2.0.0
- utils: lock the scheduler when executing hard callback functions
- utils/pyexec: add missing MP_ERROR_TEXT when compiler disabled
- utils: protect all of mpirq.c with MICROPY_ENABLE_SCHEDULER
- libc: add implementation of strncpy
- mbedtls_errors: add code to patch mbedtls for shortened error strs
- stm32lib: update library for H7 v1.6.0 and WB v1.6.0
- libm_dbl: add round.c source code
- libc: fix string0's implementation of strncpy
- timeutils: add helper functions to deal with nanosecs since 1970

drivers:
- cyw43: fix to build in nanbox mode
- cyw43: include stdio.h in files that use printf
- cyw43: return early from cyw43_wifi_set_up if wifi_on fails
- nrf24l01: change pipe addrs in test to match Arduino addrs
- onewire: fix undefined variable errors
- display/ssd1306.py: change the SET_COM_PIN_CFG setting
- support SPI/QSPI flash chips over 16MB

mpy-cross:
- main: fix stderr_print_strn parameter type
- main: print uncaught nlr jump to stderr

Support components
==================

docs:
- more consistent capitalization and use of articles in headings
- library/machine.I2C.rst: use positional-only arguments syntax
- library/machine.UART.rst: detail timeout behaviour of read methods
- README: add short paragraph about using readthedocs
- library/machine: document machine.soft_reset() function
- library: add / to indicate positional-only args in library docs
- library/uos.rst: improve block devices section, and ioctl ret vals
- esp8266: in TCP tutorial, add HTTP response code and content-type
- unix: add a new new quickref page for the UNIX port
- library: fix framebuf monochrome 1-bit modes, swapping HLSB/HMSB
- develop: detail how to add symbols to mp_fun_table for native mods
- library: add initial docs for uasyncio module
- add docs and test for uasyncio custom exc handler methods
- library: note that uasyncio.wait_for() can raise exception
- library: document that char_data/notify_data are also references
- library: note that machine.Pin.irq's hard arg may not be supported
- library: fix docs for machine.WDT to specify millisecond timeout
- develop: fix module/source name in Makefile of native example
- reference: add note about multiple exceptions when heap is locked
- library: update ubluetooth for new events and discover by uuid
- fix Sphinx 3.x warnings, and enable warnings-as-errors on build
- esp8266: add quickref documentation for UART on esp8266
- library: clarify that the arg to esp.deepsleep is in microseconds
- esp32: add info about PWM duty cycle range to esp32 quickref
- library: add gatts_indicate() doc to ubluetooth.rst
- library: for ubluetooth, add docs for _IRQ_GATTS_INDICATE_DONE
- library: update documentation of esp32's RMT
- library: update pyb.SPI init method to add descr about "ti" arg
- library: update pyb.Timer to add missing args and defaults to init
- library: update pyb.UART to correct pyboard UART availability
- esp32: fix machine.Timer quickref to specify HW timers
- change `\*` to `*` in argument lists

examples:
- accellog.py: shift long comments to their own line
- bluetooth/ble_temperature_central.py: shorten comment
- natmod: add .gitignore to ignore generated example .mpy files
- bluetooth: replace "connectable" parameter with "adv_type"
- bluetooth: fix incorrect value of BR/EDR flag in advertising
- bluetooth: fix event code in ble_temperature_central.py
- bluetooth: in ble_advertising.py, skip appearance if not set
- bluetooth: add simple UART demo with central and peripheral

tests:
- run-tests: add "--mpy-cross-flags" arg to specify mpy-cross flags
- extmod: split out VfsFat finaliser tests to separate test file
- micropython: add test for yield-from while heap is locked
- run-tests: handle 'CRASH' return by float.py feature test
- cpydiff: add CPy diff-test for using dict.keys() as a set
- unix: make unix time test pass on more platforms
- unix: add coverage test for new mp_obj_int_get_uint_checked func
- make run-tests help and README be more descriptive of behaviour
- extmod: add basic machine.Timer test
- unix: add coverage tests for pairheap data structure
- unix: add coverage test for mp_obj_new_exception_args
- unix: add coverage tests for mp_obj_is_type() and variants
- add boolean-as-integer formatting tests for fixed regression
- add tests for generator throw and yield-from with exc handlers
- basics: expand test cases for equality of subclasses
- cmdline/repl_inspect: add new test for -i option
- cmdline: add test for MICROPYINSPECT environment variable
- cpydiff: add os module environ differences
- move CPy diff test to real test now that subclass equality works
- basics: move test for "return" outside function to own file
- unix: add coverage tests for kbd-intr and scheduler
- run-tests: auto-skip extmod/ticks_diff, extmod/time_ms_us tests
- basics: add tests for equality between bool and int/float/complex
- basics: add test for equality between tuple and namedtuple
- basics: add test for tuple compare with class derived from tuple
- basics/array1.py: add equality testing for array
- run-multitests.py: add new test runner for multiple Py instances
- multi_net: add initial set of multi-instance tests for network
- multi_bluetooth: add initial tests for bluetooth BLE
- run-tests: consider all tests as native when emit=native is used
- run-multitests.py: print test summary and do exit(1) on failure
- extmod: add uasyncio tests
- run-tests: skip uasyncio if no async, and skip one test on native
- make default MICROPYPATH include extmod to find uasyncio
- multi_net: add uasyncio test for TCP server and client
- net_inet: add uasyncio internet tests
- basics/dict_pop.py: remove extra comma in call and fix grammar
- micropython/heapalloc_fail_set.py: remove extra trailing comma
- format all Python code with black, except tests in basics subdir
- float: add new lexer test to test parsing of float without prefix
- run-tests: add commands to print and clean *.exp,out files
- extmod: update littlefs test output to match new library version
- run-tests: make diff tool user configurable
- float: fix cmath_fun_special for MICROPY_FLOAT_IMPL_FLOAT
- extmod: add btree test for errors raised by btree DB library
- run-multitests.py: allow filtering out lines from stdout
- multi_bluetooth/ble_gap_advertise: fix bytes/str compare warning
- run-multitests.py: add shortcuts for local Python instances
- cpydiff: add cpydiff test for __all__ used in imported package
- thread/thread_stacksize1.py: increase stack size for CPython
- multi_bluetooth: fix typo printing wrong IRQ type
- run-multitests.py: add TRACE banner and move TEST output to end
- run-tests: skip REPL feature checks when running via pyboard.py
- multi_bluetooth: update to work with new BLE events
- run-multitests.py: allow passing unique env vars to each instance
- basics: add tests for assignment operator :=
- cpydiff: add CPy diff test for assignment expression behaviour
- basics: add tests for variable annotations
- basics: split out memoryview slice-assign tests to separate file
- move .mpy import tests from import/ to micropython/ dir
- micropython: improve .mpy import tests to run on more targets
- extmod: add test for uasyncio.sleep of a negative time
- extmod: make uasyncio_fair test more reliable by adjusting sleeps
- run-tests: use absolute paths where possible
- run-tests: make test output directory configurable
- split out complex reverse-op tests to separate test file
- extmod: add tests for verifying FAT and littlefs mtime values

tools:
- gen-cpydiff.py: adjust subsections to sentence case
- add metrics.py script to build and compute port sizes/metrics
- pydfu.py: clean up syntax, update comments and docstrings
- pyboard.py: add option --no-follow to detach after sending script
- pyboard.py: use slice del instead of list.clear() for Py2 compat
- pyboard.py: change shebang to use python3
- makemanifest.py: support freezing with empty list of mpy files
- codeformat.py: add formatter using uncrustify for C, black for Py
- makemanifest.py: fix build on Windows by adding .exe to mpy-cross
- metrics.py: use check_call instead of run to error out on error
- codeformat.py: eliminate need for sizeof fixup
- pydfu.py: add args for VID/PID & exit with cleaner error handling
- pydfu.py: display any error strings from device/mboot
- codeformat.py: include all msvc C code in auto-format
- pyboard.py: support setting device/baudrate from shell env vars
- pyboard.py: add -d as an alias for --device
- metrics.py: add option to diff to error if delta above threshold
- metrics.py: don't build mpy-cross if not needed by any ports
- metrics.py: use OrderedDict when reading build log
- check_code_size.sh: remove unused script
- codeformat.py: use -q option on uncrustify to make output quiet
- codeformat.py: add verbose option to pass to uncrustify and black
- uncrustify.cfg: remove deprecated sp_word_brace option
- codeformat.py: remove sizeof fixup
- uncrustify: update config for v0.71.0
- codeformat.py: include extmod/{btstack,nimble} in code formatting
- uncrustify: enable more opts to remove space between func and '('
- makemanifest.py: support freezing a subdirectory recursively
- pydfu.py: respect longer timeouts requested by DFU device/mboot
- makemanifest.py: use errno.EEXIST instead of number 17
- makemanifest.py: print nicely formatted errors from mpy-cross
- pyboard.py: replace eval() of received data with alternative
- mpy-tool.py: fix offset of line number info
- makemanifest.py: use os.makedirs to make path for generated files

CI:
- add new job to build and test unix coverage in 32-bit mode
- add stm32 build in nanbox mode
- update travis to specify which unix variant to build
- add OSX build to CI
- add CI job to check code formatting
- build stm32 PYBD_SF6 with BTstack as bluetooth stack
- run multi_net tests as part of coverage job
- for unix tests use Makefile target instead of explicit commands
- print errors out for OSX job
- exclude some uasyncio tests on OSX
- use custom PPA to get pre-built uncrustify
- use grep with --text on qemu-arm output
- build NUCLEO_L073RZ instead of B_L072Z_LRWAN1 for stm32 job
- build full unix coverage build on osx job
- build GENERIC_1M board as part of esp8266 job
- make OSX build work again by not installing pkgconfig
- split esp32 ESP-IDF v3 and v4 builds to separate jobs
- decrease build duration by starting OSX build early
- finish jobs early after test failure
- use tools/metrics.py to compute size diff of minimal ports
- make sure upstream/master exists when computing size-diff check
- build more boards as part of nrf job
- run apt commands once, to slightly speed up the CI
- set build name so it appears in the web interfaces
- for powerpc job, build both UART variants
- change nrf pca10056 board to build with soft-device enabled
- build qemu-arm with MP_ENDIANNESS_BIG=1 to test bigendian build
- in stm32 job, build mboot for NUCLEO_WB55
- build mboot for PYBV10 with LFS2 enabled in stm32 job
- install newer toolchain for nrf job
- add pca10090 build to nrf job
- change nrf pca10056 board to build with s140 SoftDevice
- add zephyr build to CI
- add GitHub action to build docs

The ports
=========

all ports:
- allow overriding CROSS_COMPILE in a custom makefile
- modify mp_hal_pin_write macro so it can be used as a function
- add lib/libm/roundf.c to bare-metal Makefile's
- enable error text compression for various ports, but not all
- disable MICROPY_PY_ASSIGN_EXPR in bare-arm and minimal ports

cc3200 port: no changes specific to this port

esp8266 port:
- modules: fix AttributeError in _boot.py if flash not formatted
- modules/ntptime.py: add comment about configuring NTP host
- put mp_keyboard_interrupt in IRAM
- machine_pin: disable ets_loop_iter during hard IRQ handler
- modmachine: implement machine.soft_reset()
- README.md: add docker build instructions
- modnetwork: add support for wlan.ifconfig('dhcp')
- enable and freeze uasyncio
- change from FAT to littlefs v2 as default filesystem
- makeimg.py: print out info about RAM segments when building fw
- machine_pin: move pin_intr_handler to iRAM, de-support hard IRQ
- mpconfigport.h: add definitions for BEGIN/END_ATOMIC_SECTION
- clean up Pin intr handler by moving all code to machine_pin.c
- boards: move py/pairheap.c code from iRAM to iROM
- esp_mphal: move most functions in esp_mphal.c from iRAM to iROM
- uart: move a few functions from iRAM to iROM
- boards: allow configuring btree/FAT/LFS2 support when building
- esppwm: fix PWM glitch when setting duty on different channel

esp32 port:
- Makefile: assign result of $call to dummy var for older make
- modmachine: add implementation of machine.soft_reset()
- enable NimBLE support on all builds (IDF 3.3 and 4.0)
- modnetwork: add max_clients kw-arg to WLAN.config for AP setting
- Makefile: reorder includes to build with latest toolchain
- uart: use core-provided mp_keyboard_interrupt, placed in IRAM
- modsocket: convert EADDRINUSE error code from lwip return value
- move to IDF 4.0 release version
- deinitialize Bluetooth on soft reset
- README.md: update build instructions for newer toolchain
- modsocket: handle poll of a closed socket
- enable and freeze uasyncio
- README.md: fix typo in venv instructions
- change from FAT to littlefs v2 as default filesystem
- espneopixel: use integer arithmetic to compute timing values
- update to ESP IDF v3.3.2
- modesp32: add idf_heap_info(capabilities) to esp32 module
- consolidate check_esp_err functions and add IDF error string
- improve support for OTA updates
- partitions: update comments in files regarding offset
- modsocket: fix getaddrinfo to raise on error
- machine_sdcard: add "freq" keyword arg to SDCard constructor
- modmachine: fix machine.reset_cause to use IDF's esp_reset_reason
- mpthreadport: fix calculation of thread stack size
- update IDF v4.0 supported hash to v4.0.1
- esp32_rmt: extend RMT to support carrier feature
- esp32_rmt: call rmt_driver_install before rmt_config
- esp32_rmt: properly fix looping behaviour of RMT
- network_lan: add support for IP101 PHY
- mphalport: fix mp_hal_time_ns offset

javascript port: no changes specific to this port

mimxrt port:
- add new, minimal port to NXP i.MX RT series CPUs
- add MIMXRT1010 board
- add MIMXRT1060_EVK board
- add initial impl of machine.LED class, and basic pin support
- tusb_config.h: preliminary fix for TinyUSB HS endpoint overflow
- boards: enable LED class for MIMXRT1060_EVK board
- boards: integrate support for MIMXRT1020_EVK board
- boards: set __heap_size__ to 0 in MIMXRT1011.ld

minimal port:
- make build more flexible and work as 64-bit build

nrf port:
- main: remove unnecessary repl_info(0) call
- boards/common.ld: add ENTRY(Reset_Handler) in linker script
- drivers: use mp_raise_msg where appropriate, and shorten exc msgs
- drivers/bluetooth: fix variable initialisation error with older gcc
- remove custom "random" module and use extmod version instead
- use MICROPY_HW_ENABLE_RNG instead of MICROPY_PY_RANDOM_HW_RNG
- Makefile: don't use -fno-builtin for Cortex-M0 builds
- mphalport: remove need for "syntax unified" in mp_hal_delay_us
- update to work with nrfx v2.0.0, to match TinyUSB
- add openocd as a supported flasher
- bluetooth: use MP_ERROR_TEXT for all error messages
- bluetooth/ble_uart: fix implicit declaration of function
- bluetooth: handle data length update request
- bluetooth/ble_uart: add mp_hal_stdio_poll function
- bluetooth/ble_uart: fix random advertisement name
- bluetooth/ble_uart: swap end character on cooked strings
- Makefile: disable ROM text compression when compiling for debug
- add support for time.ticks_xxx functions using RTC1
- enable nrf tick support on all boards by default
- boards: add initial support for Actinius Icarus
- nrfx_config: disable RTC2 for nRF9160 targets
- boards: enable RTCounter machine module for nrf9160 boards
- add board definition for nRF52840-MDK-USB-Dongle
- split mpconfigport.h into multiple files
- enable more features for all targets
- Makefile: improve user C modules support

pic16bit port: no changes specific to this port

powerpc port:
- fix Makefile rule when linking
- set better default compiler
- uart: choose which UART to use at build time, not runtime

qemu-arm port:
- set default board as mps2-an385 to get more flash for tests
- README: update link to toolchain
- support building in debug mode with DEBUG=1
- Makefile: add CFLAGS_EXTRA to CFLAGS

samd port:
- fix to build with latest tinyusb

stm32 port:
- mbedtls: resize mbedtls output buffer from 16 down to 4 kiB
- fix to build in nanbox mode
- add configuration to build in nanbox mode
- boards/PYBD: change RTC asynch prediv from 1 to 4
- softtimer: change linear linked list to a pairing heap
- powerctrl: for F7, allow PLLM!=HSE when setting PLLSAI to 48MHz
- Makefile: allow a board's .mk file to add things to CFLAGS
- boards/STM32F769DISC: add config to use external SPI as filesys
- powerctrl: disable HSI if not needed to save a bit of power
- powerctrl: enable overdrive on F7 when waking from stop mode
- boards/stm32f746_af.csv: add ADC alt functions to correct pins
- sdio: add support for H7 MCUs
- stm32_it: don't call __HAL_USB_HS_EXTI_CLEAR_FLAG on H7 MCUs
- powerctrl: improve support for changing system freq on H7 MCUs
- powerctrl: reenable PLL3 on H7 MCUs when waking from stop mode
- sdram: expose the result of sdram startup test in stm32_main
- usbd_conf: allow boards to configure USB HS ULPI NXT/DIR pins
- usbd_cdc_interface: remove "interrupt_char != -1" check
- sdram: fix compile issue from unused sdram startup test flag
- mpconfigport.h: add option to have custom help text
- modnetwork: remove redundant call to nimble_poll in lwip poll
- refactor bluetooth stack/hci/driver bindings
- add bindings for BTstack implementation
- boards/PYBD: allow building with BTstack (via make command line)
- refactor Bluetooth HCI RX to be independent of transport layer
- main: fix bug mounting 3rd SD partition
- mboot: allow overriding led_init and led_state in board folder
- mboot: update dfu state/status flags to better match standard
- mboot: protect against invalid address flash writes
- mboot: update LED0 state from systick handler
- mboot: remove unnecessary test for led being 1 in led_state
- softtimer: initialise pairing-heap node before pushing to heap
- enable and freeze uasyncio
- mpconfigport.h: remove unused root pointer for BTstack bindings
- mpconfigport.h: make most extended modules configurable by board
- boards: disable pend_throw, uheapq, utimeq on small-flash boards
- Makefile: add missing ordering dependency on generated headers
- storage: fix start address of second, internal block device
- mboot/README: clarify that mboot can access FAT formatted FS only
- mboot: expose custom DFU USB VID/PID values at makefile level
- Makefile: rename SRC_LIB to LIB_SRC_C to match other ports
- main: peform a clean shutdown of btstack on soft reset
- boards/PYBD_SF2: put BTstack library in external QSPI XIP flash
- README: reorg DFU flashing instructions with addition for PYBD
- add support for F412 MCUs
- boards: add board config for Nucleo-F412ZG development board
- machine_uart: retain attached-to-repl setting when init'ing UART
- machine_uart: allow re-init'ing a static UART object
- modmachine: allow changing AHB and APB bus frequencies on STM32WB
- adc: add support to pyb.ADC for STM32WB MCUs
- machine_adc: make setting of ADC1_COMMON->CCR clearer on STM32WB
- dma: add support for DMA on STM32WB, with SPI settings provided
- boards/xxx_WB55: enable pyb.ADC and hardware SPI on WB55 boards
- Makefile: quote libgcc path so spaces are not an issue
- boards/STM32F769DISC: use macro instead of const for flash size
- factoryreset: provide empty create-FS function when FAT disabled
- usb: add support for 2xVCP on L0, L432 and WB MCUs
- rfcore: leave txpower level as default when initialising rfcore
- boards/NUCLEO_WB55: add more CPU pins and aliases to SW1/2/3
- irq: clean up irq.h so it does not depend on core uPy defines
- powerctrlboot: include irq.h to get definitions of IRQ priorities
- flash: make flash C-API reusable, and funcs return an error code
- i2cslave: add support for WB MCUs
- flash: add flash_is_valid_addr, and extend sectors for 2MB F7
- mboot: use flash routines from main stm32 code rather than custom
- mboot: use CMSIS system source code for SystemInit function
- mboot: add support for using mboot with WB MCUs
- boards: add build-time option for NUCLEO_WB55 to use mboot
- mboot: set VTOR on start up to ensure it has the correct value
- mboot: use additional CFLAGS to compile string0.c
- mpconfigport.h: enable PY_IO_FILEIO when any VFS is enabled
- timer: support TIM1 on WB MCUs
- boards: enable LFS2 on PYBD_SF3 and PYBD_SF6
- mboot: don't search for firmware on FS, just attempt to open it
- mboot: decouple stream, filesystem and top-level loading code
- mboot: add support for littlefs
- mboot: update README to describe WB and littlefs support
- i2cslave: pass I2C instance to callbacks to support multi I2Cs
- usbd_cdc_interface: remove full==size-1 limitation on tx ringbuf
- timer: properly initialise timer deadtime/brk on WB MCUs
- mboot: implement DFU mass erase
- flash: update flash_get_sector_info to return -1 on invalid addr
- mboot: add DFU logic to respond to DFU_GETSTATE request
- mboot: remove the use of timeout in DFU_GETSTATUS
- mboot: disable polling mode by default and use IRQ mode instead
- fdcan: use the right FIFO to calc element address in can_receive
- fdcan: use FDCAN_RXFxS_FxFL instead of hard-coded value
- fdcan: support maximum timeout of HAL_MAX_DELAY in can_receive
- pyb_can: handle timeout arg for FDCAN in pyb_can_send
- usbdev: fix calculation of SCSI LUN size with multiple LUNs
- pin_defs_stm32: fix pin printing to show IN mode correctly
- powerctrl.h: include stdbool.h to get definition of bool

teensy port: no changes specific to this port

unix port:
- modtime: add utime.mktime function, to complement utime.localtime
- modos: add uos.rename and uos.rmdir
- add build variants, analogous to boards on bare-metal
- add placeholder DEV variant with settrace enabled
- rename unix binaries to micropython-variant (not _variant)
- Makefile: reserve CFLAGS_EXTRA/LDFLAGS_EXTRA for external use
- release GIL during all system calls
- unix_mphal: add compile check for incompatible GIL+ASYNC_KBD_INTR
- main: print usage and NLR errors to stderr instead of stdout
- main: add support for MICROPYINSPECT environment variable
- main: add #if guard around -v option usage and document -i/-m opts
- main: add command-line -h option for printing help text
- modos: implement putenv and unsetenv to complement getenv
- main: use OS-dependent path separator when searching path
- Makefile: remove old variant targets that are no longer needed
- variants/standard: fix role of PREFIX when used to install
- Makefile: allow to install all variants of the executable
- mpthreadport: use SIGRTMIN+5 instead of SIGUSR1 for thread-GC
- mpthreadport: fix Mac build by using SIGUSR1 if SIGRTMIN not avail
- mphalport.h: fix build when MICROPY_USE_READLINE=0
- unix_mphal: adjust #if in mp_hal_stdin_rx_chr to improve format
- file: don't raise OSError(EINVAL) on sys.stdin/out/err.flush()
- Makefile: detect and pass thru mpy-cross flags when running tests
- remove custom file implementation to use extmod's VFS POSIX one
- remove custom definition of MP_PLAT_PRINT_STRN
- coverage: init all pairheap test nodes before using them
- enable uasyncio C helper module on coverage build
- mpthreadport: fix crash when thread stack size <= 8k
- implement PEP 475 to retry syscalls failing with EINTR
- mpthreadport: ensure enough thread stack to detect overflow
- fix behaviour of COPT/NDEBUG for unix variants
- implement MICROPY_BEGIN/END_ATOMIC_SECTION protection macros
- Makefile: fix regression using install on non-GNU systems
- modmachine: add machine.idle(), implemented using sched_yield
- add support for modbluetooth and BLE using btstack
- enable modbluetooth on the "dev" and "coverage" variants
- add btstack to the unix submodules list
- main: enter REPL when inspect active, even with stdin redirected
- btstack_usb: allow choosing adaptor via environment variable
- make manifest selection match other ports
- enable uasyncio on dev variant
- variants: enable VFS and all supported filesystems on dev variant
- make the MICROPY_xxx_ATOMIC_SECTION mutex recursive
- fatfs_port: implement get_fattime
- variants: fix fast and freedos variants so they build again
- modos: support larger integer range in uos.stat fields

windows port:
- support word-based move/delete key sequences for REPL
- windows_mphal: release GIL during system calls
- improve default search path
- msvc: fix warnings regarding function declarations
- remove custom definition of MP_PLAT_PRINT_STRN
- windows_mphal: fix missing semicolon
- update genhdr.targets to match makeqstrdefs.py args
- make appveyor.yml self-contained

zephyr port:
- update include paths for Zephyr v2.0
- replace deprecated time conversion macro
- remove reference to syscall_macros_h_target
- implement block device protocol via zephyr disk access api
- enable virtual file system and uos module
- enable fatfs
- implement block device protocol via zephyr flash map api
- enable littlefs
- mount a file system during init
- enable usb mass storage class on mimxrt1050_evk
- execute main.py file if it exists
- update machine.Pin class to use new zephyr gpio api
- use zephyr build system to merge configurations
- fix and rename stacks_analyze function in zephyr module
- fix floating point configuration
- update for refactored zephyr device structures
- update to new zephyr timeout API
- convert DT_FLASH_AREA usages to new dts macros
- increase minimum required cmake version to 3.13.1
- use cmake find_package to locate zephyr
- implement machine.Pin.irq() for setting callbacks on pin change
- make-minimal: disable FAT and LFS2 options to make it build
- include storage/flash_map.h unconditionally
- README: update required Zephyr version and mention new features

PYBD boards, BLE and littlefs, dynamic native modules, samd and powerpc

This release sees a reduction in overall bytecode size due to compression
of the bytecode prelude, saving 7 bytes of bytecode per function for
roughly 80% of functions.  The bytecode opcode values are also redefined to
group them based on their argument size and format.  Support is also added
for the matrix multiplication operator "@" (PEP 465).

The .mpy file format moved to version 5 to support the new bytecode
encoding, and added support for relocation of native machine code, along
with separate rodata and BSS sections.  This allows a MicroPython system to
import dynamic native modules, .mpy files that are generated from C code.
Examples of this feature are provided in "examples/natmod/" and
documentation in "docs/develop/natmod.rst".

Some code-size saving optimisations were implemented leading to a reduction
in size of minimal firmware: bare-arm reduced by 584 bytes, minimal x86 by
5476 bytes (partly due to changed compiler optimisation flags) and minimal
ARM Thumb 2 by 1440 bytes (all measured with gcc 9.2.0).

A new mechanism to freeze scripts into firmware is provided - a frozen
manifest - whereby scripts to freeze are listed in a Python file (eg
manifest.py).  All ports are updated to use this new feature.

When weak module links are enabled (via MICROPY_MODULE_WEAK_LINKS) an
import will now automatically search for the built-in u-variant of a module
if the non-u-variant fails (eg searches for "ufoo" if "foo" fails), so
ports no longer provide an explicit list of these.  The unix and windows
ports now enable this feature.

A performance benchmarking test suite is added which can be used to compare
changes in absolute performance when optimising features, as well as
compare across different ports.  See "tests/run-perfbench.py".

Bluetooth (BLE only) support is added via the "ubluetooth" module and
provides the ability to implement the four BLE roles.  The BLE stack is
used is Mynewt Nimble and it currently runs on PYBD boards, STM32WB55 MCUs
and ESP32 boards.

Support for littlefs filesystems is added through the MicroPython VFS
interface, and it works on the unix, stm32, esp8266 and esp32 ports.

A new "machine.ADC.read_u16()" method is defined and implemented on stm32,
esp8266, esp32 and nrf ports, providing a consistent way to read an ADC
that returns a value in the range 0-65535.  This new method should be
preferred to the existing "ADC.read()" method.

The stm32 port sees support for the new PYBD range of pyboards which
include a fully integrated CYW43xx WiFi/BT chip.  USB is enhanced to
support VCP+MSC+HID mode and up to 3x simultaneous VCP interfaces.  Support
is also added for STM32WBxx MCUs including BLE.  There is a new machine.ADC
class which is compatible with other ports, along with a new machine.Timer
class that implements a software timer with millisecond resolution and
number of active timers only limited by RAM.  Support for littlefs is
available by default via uos.VfsLfs2.  Documentation for using littlefs is
found in "docs/reference/filesystem.rst".

The esp8266 port has switched to use per-board configurations and builds,
as well as the new frozen manifest feature.  It also has optional littlefs
support (requires a separate build).

The esp32 port has the following new features: native code generation,
machine.SDCard, hardware I2C, mDNS queries and responder, esp32.Partition,
esp32.RMT, BLE (requires IDF v4), and built-in support for VfsLfs2.  It has
switched to use per-board configurations and builds, and frozen manifests.
The default SSL output buffer is resized from 16kiB down to 4kiB to save
RAM.

There are new, minimal ports to Microchip SAMDxx microcontrollers, and
the bare metal PowerPC architecture.

A code-of-conduct based on the PSF's code is added in CODEOFCONDUCT.md.

The following new Git submodules are added: mbedtls, asf4, tinyusb,
mynewt-nimble.  And a new third-party library: littlefs.

A detailed list of changes follows.

py core:
- nativeglue: make private glue funs all static, remove commented code
- nativeglue: remove dependency on mp_fun_table in dyn-compiler mode
- obj: optimise small-int comparison to 0 in mp_obj_is_true
- nlrthumb: save and restore VFP registers s16-s21 when CPU has them
- mkrules.mk: use $(CPP) not $(CC) -E for preprocessor rule
- define EMIT_MACHINE_CODE as EMIT_NATIVE || EMIT_INLINE_ASM
- persistentcode: fix compilation with load and save both enabled
- persistentcode: ensure prelude_offset is always initialised
- asmarm: use __clear_cache on Linux/GCC when creating new asm code
- nlrthumb: check __thumb2__ instead of __ARM_ARCH_6M__
- objgenerator: add missing #if guard for PY_GENERATOR_PEND_THROW
- asmarm: use __builtin___clear_cache instead of __clear_cache
- makeqstrdata.py: allow using \r\n as a qstr if a port requires it
- scheduler: rename sched_stack to sched_queue
- objstringio: guard bytesio_stream_p struct w/ MICROPY_PY_IO_BYTESIO
- objdict: quote non-string types when used as keys in JSON output
- builtinimport: populate __file__ when importing frozen or mpy files
- runtime: allow to override builtins.__import__ with Python func
- modio: call mp_import_name to do resource stream import
- allow to pass in read-only buffers to viper and inline-asm funcs
- showbc: fix off-by-one when showing address of unknown opcode
- implement new sys.atexit feature
- objarray: fix amount of free space in array when doing slice assign
- modmath: implement math.isclose() for non-complex numbers
- introduce MP_UNREACHABLE macro to annotate unreachable code
- nlr: use MP_UNREACHABLE at the end of arch-specific nlr_jump funcs
- compile: improve the line numbering precision for comprehensions
- emitbc: rewrite switch in load_const_tok to reduce code size
- emitbc: make all emit_write_bytecode_* funcs take a stack_adj arg
- objgenerator: move defn of mp_const_GeneratorExit_obj here
- vm: shorten error message for not-implemented opcode
- vm: don't add traceback info for exc's propagated through a finally
- vm: don't add traceback info for exceptions that are re-raised
- add global default_emit_opt variable to make emit kind persistent
- compile: improve the line numbering precision for lambdas
- bc: factor out code to get bytecode line number info into new func
- profile: add initial implementation of sys.settrace feature
- integrate sys.settrace feature into the VM and runtime
- profile: add debugging for sys.settrace feature
- objtuple: allow compatible subclasses of tuple in mp_obj_tuple_get
- modstruct: fix struct.unpack with unaligned offset of native type
- modstruct: fix struct.pack_into with unaligned offset of native type
- binary: change mp_uint_t to size_t for index, size, align args
- bc: fix size calculation of UNWIND_JUMP opcode in mp_opcode_format
- mkenv.mk: add GDB variable
- vm: factor cached map lookup code to inline function
- mkrules.mk: add QSTR_GLOBAL_REQUIREMENTS variable for qstr auto-gen
- persistentcode: enable persistent code saving for Windows ports
- lexer: reorder operator tokens to match corresponding binary ops
- parse: use calculation instead of table to convert token to operator
- compile: use calculation instead of switch to convert token to op
- add support for matmul operator @ as per PEP 465
- bc0: order opcodes into groups based on their size and format
- bc: replace big opcode format table with simple macro
- introduce and use constants for multi-opcode sizes
- split RAISE_VARARGS opcode into 3 separate ones
- nlr.h: factor out constants to specific macros
- emitnative: factor sizeof/offsetof calculations to macros
- rename MP_QSTR_NULL to MP_QSTRnull to avoid intern collisions
- nativeglue: make mp_fun_table fixed size regardless of config
- persistentcode: bump .mpy version to 5
- ringbuf: add helpers for put16/get16
- bc: change mp_code_state_t.exc_sp to exc_sp_idx
- add n_state to mp_code_state_t struct
- compress first part of bytecode prelude
- rework and compress second part of bytecode prelude
- bc: don't include mp_decode_uint funcs when not needed
- compile: disallow 'import *' outside module level
- makeqstrdefs.py: remove unused blacklist
- vm: fix handling of unwind jump out of active finally
- runtime: fix PEP479 behaviour throwing StopIteration into yield from
- emitnative: add support for archs with windowed registers
- emitnative: add support for using setjmp with native emitter
- emitnative: add support for archs that cannot read executable data
- asmxtensa: add support for Xtensa with windowed registers
- add new Xtensa-Windowed arch for native emitter
- persistentcode: make .mpy more compact with qstr directly in prelude
- objtype: add type.__bases__ attribute
- mkrules.mk: add warning/error for invalid frozen config
- objstr: size-optimise failure path for mp_obj_str_get_buffer
- automatically provide weak links from "foo" to "ufoo" module name
- modarray: rename "array" module to "uarray"
- runtime: reorder some binary ops so they don't require conditionals
- stream.h: add MP_STREAM_POLL_NVAL constant
- nativeglue: remove unused mp_obj_new_cell from mp_fun_table
- objgenerator: remove globals from mp_obj_gen_instance_t
- objgenerator: allow pend_throw to an unstarted generator
- persistentcode: move declarations for .mpy header from .c to .h file
- modsys: report .mpy version in sys.implementation
- emitnative: fix typo, REG_PARENT_ARG_RET should be REG_PARENT_RET
- emitnx86: make mp_f_n_args table match order of mp_fun_kind_t
- objdict: support ujson.dump() of OrderedDict objects
- ringbuf: add peek16 method
- compile: coalesce error message for break/continue outside loop
- builtinimport: raise exception on empty module name
- qstr: raise exception in qstr_from_strn if str to intern is too long
- objstringio: slightly optimize stringio_copy_on_write for code size
- objenumerate: check for valid args in enumerate constructor
- persistentcode: add ability to relocate loaded native code
- nativeglue: add new header file with native function table typedef
- nativeglue: add funcs/types to native glue table for dynamic runtime
- persistentcode: make ARM Thumb archs support multiple sub-archs
- nativeglue: add float new/get functions with both single and double
- dynruntime: add support for float API to make/get floats
- dynruntime: implement uint new/get, mp_obj_len and mp_obj_subscr
- persistentcode: move loading of rodata/bss to before obj/raw-code

extmod:
- add network-level class binding to cyw43 driver
- factor out makefile rules from py.mk to new extmod.mk file
- extmod.mk: integrate mbedTLS so it is built from source
- modussl_mbedtls: allow to build with object representation D
- extmod.mk: include mdns app source in lwIP build
- uos_dupterm: add mp_uos_dupterm_poll to poll all dupterms
- moduwebsocket: make close_resp static array const to not use RAM
- modwebrepl: make prompt/ver static arrays const to not use RAM
- modwebrepl: add config option to put filebuf[512] on stack/bss
- modlwip: for TCP send keep trying tcp_write if it returns ERR_MEM
- modlwip: use mp_sched_schedule to schedule socket callbacks
- modlwip: implement raw sockets for lwIP
- modure: make regex dump-code debugging feature optional
- moducryptolib: use "static" not "STATIC" for inline functions
- give vars/funcs unique names so STATIC can be set to nothing
- modujson: support passing bytes/bytearray to json.loads
- crypto-algorithms: add source to header and populate copyright
- vfs_posix: include stdio.h for declaration of function 'rename'
- nimble: add nimble bindings
- modbluetooth: add low-level Python BLE API
- modbluetooth_nimble: implement modbluetooth API with Nimble
- modbluetooth_nimble: use random addr if public isn't available
- modbluetooth: allow MP_BLUETOOTH_MAX_ATTR_SIZE in board config
- modbluetooth: allow config of scan interval/window
- modbluetooth: use us instead of ms for advertising interval
- modbluetooth: increase maximum connections from 1 to 4
- modbluetooth: clear gap_advertise payload when data is empty
- modbluetooth: fix order of params to IRQ_GATTS_WRITE event
- modbluetooth: improve ringbuf handling
- modbluetooth: make gap_disconnect not raise when disconnected
- modbluetooth: in gap_advertise only accept None to stop adv
- re1.5: support escaping within RE classes
- modbluetooth: make UUID support the buffer protocol
- modbluetooth: persist reference to NimBLE service instances
- modbluetooth_nimble: use `data_alloc` length to truncate writes
- modbluetooth: rename module to "ubluetooth"
- factor out block-device struct to make independent of fatfs
- vfs_blockdev: factor out block device interface code
- vfs_blockdev: add extended read/write methods
- add VFS littlefs bindings
- vfs: rename BP_IOCTL_xxx constants to MP_BLOCKDEV_IOCTL_xxx
- vfs: add MP_BLOCKDEV_IOCTL_BLOCK_ERASE constant
- modbluetooth: add gatts_set_buffer
- vfs_lfs: allow compiling in VfsLfs1 and VfsLfs2 separately
- modlwip: unconditionally return POLLHUP when polling new socket
- modlwip: make socket poll return POLLNVAL in case of bad file
- modlwip: unconditionally return POLLHUP/POLLERR when polling
- modussl_mbedtls: fix getpeercert to return None if no cert avail
- modussl_mbedtls: check for invalid key/cert data
- nimble: remove unneeded nimble_sprintf wrapper function
- nimble: factor out stm32-specific HCI UART RX/TX code
- modbtree: make FILEVTABLE const to put it in ROM
- convert nlr_raise(mp_obj_new_exception_msg(x)) to mp_raise_msg(x)
- vfs: add autodetect of littlefs filesystem when mounting
- consolidate FAT FS config to MICROPY_VFS_FAT across all ports
- modbluetooth: prioritise non-scan-result events
- modbluetooth: create UUID from bytes and allow comparison ops
- modbluetooth_nimble: make gap_scan_stop no-op if no scan ongoing
- modbluetooh_nimble: fix UUID conversion for 16 and 32 bit values
- modbluetooth: simplify management of pre-allocated event data
- vfs_lfs: pass flag along to ioctl when init'ing bdev for lfs
- vfs_lfs: fix bug when passing no args to constructor and mkfs
- modbluetooth: simplify how BLE IRQ callback is scheduled
- modbluetooth: remove limit on data coming from gattc data input
- modbluetooth: add optional 4th arg to gattc_write for write mode
- modbluetooth: allow setting ringbuf size via BLE.config(rxbuf=)
- modbtree: use mp_printf instead of printf
- add dynamic-runtime guards to btree/framebuf/uheapq/ure/uzlib
- webrepl: move webrepl scripts to common place and use manifest

lib:
- cmsis: upgrade to CMSIS 5.5.1
- netutils: add DHCP server component
- add new submodule for mbedtls, currently at v2.17.0
- utils/sys_stdio_mphal: add support to poll sys.stdin and sys.stdout
- add asf4 as a submodule
- add tinyusb as a submodule
- stm32lib: update library for updated H7xx, new L0xx, new WBxx
- lwip: update lwIP to v2.1.2, tag STABLE-2_1_2_RELEASE
- mynewt-nimble: add Apache mynewt nimble as a submodule
- littlefs: add littlefs v1.7.2 source
- littlefs: add littlefs v2.1.3 source
- littlefs: add README describing origin and how to gen lfs1/lfs2
- libc/string0: add simple implementations of strspn and strcspn

drivers:
- add driver for CYW43xx WiFi SoCs
- memory/spiflash: add support to put SPI flash in sleep mode
- cyw43: add low-level CYW43xx Bluetooth HCI UART driver
- onewire/ds18x20.py: add support for DS1822 sensor
- sdcard: raise exception on timeout of readinto
- wiznet5k: allow selecting maximum fixed buffer size for MACRAW

tools:
- mpy-tool.py: fix linking qstrs in native code, and multiple files
- mpy-tool.py: fix linking of qstr objects in native ARM Thumb code
- add uf2conv.py from Microsoft/uf2 repository
- pyboard.py: add filesystem commands to ls/cat/cp/rm remote files
- mpy-tool.py: force native func alignment to halfword/word on ARM
- mpy-tool.py: add initial support for frozen with settrace
- mpy-tool.py: fix freezing of non-bytecode funcs with settrace
- make-frozen.py: allow to run with no directory passed in
- add mechanism to provide a manifest of frozen files
- makemanifest.py: eval relative paths w.r.t. current manifest file
- mpy-tool.py: use "@progbits #" attribute for native xtensa code
- makemanifest.py: follow symlinks when freezing linked directories
- makemanifest.py: skip freezing unsupported files with warning
- makemanifest.py: use sys.executable when invoking Python scripts
- mpy-tool.py: support qstr linking when freezing Xtensa native mpy
- mpy-tool.py: add ability to merge multiple .mpy files into one
- mpy_ld.py: add new mpy_ld.py tool and associated build files
- mpy-tool.py: raise exception if trying to freeze relocatable mpy
- pyboard.py: support executing .mpy files directly
- tinytest-codegen.py: add extra newline and result message

tests:
- rename "bench" tests to "internal_bench" and run-internalbench.py
- add performance benchmarking test-suite framework
- perf_bench: add some benchmarks from python-performance
- perf_bench: add some miscellaneous performance benchmarks
- perf_bench: add some viper performance benchmarks
- stress/recursive_iternext.py: increase large depth to 5000
- run-perfbench.py: add --emit option to select emitter for tests
- add tests for overriding builtins.__import__
- misc/sys_atexit: add test for new sys.atexit feature
- unix: update extra_coverage expected output with new atexit func
- extmod: split json.loads of bytes/bytearray into separate test
- split out test for optimisation level and line-no printing
- add tests for sys.settrace feature
- basics: add test for matmul operator
- update tests for changes to opcode ordering
- micropython: add test for native generators
- basics: add test for getting name of func with closed over locals
- basics: add test for throw into yield-from with normal return
- perf_bench: add bm_fft test
- run-perfbench.py: show error when truth check fails
- run-perfbench.py: skip complex tests if target doesn't enable it
- cpydiff: fix typo in types_bytes_keywords.py doc comments
- rename "array" module to "uarray"
- extmod: add littlefs tests
- extmod: add test for blockdev with standard and extended protocol
- basics: use str.format instead of % for formatting messages
- basics/builtin_dir.py: look for "version" in dir(sys)
- add feature check for bytearray and skip corresponding tests
- basics: split out specific bytearray tests to separate files
- basics: use bytes not bytearray when checking user buffer proto
- add feature check for slice and skip corresponding tests
- basics: split out specific slice tests to separate files
- run-tests: add misc list of tests that use slice, to skip them
- basics: automatically skip tests that use str/bytes modulo-format
- add feature check for uio module and skip corresponding tests
- basics: split sys.exit test to separate file so it can be skipped
- extmod: add test for ussl when passing in key/cert params
- stress: add test for maximum length limit of qstrs
- import: add test for importing viper code with additional flags
- add script to run dynamic-native-module tests
- add .exp files for basics/parser and import/import_override
- stress/qstr_limit: tune params to run with stm32 port
- basics/memoryview_itemsize: make portable to 32- and 64-bit archs
- extmod/vfs_lfs_error: use small ints in seek error test
- pyb: refactor pyboard tests to work on PYBv1, PYBLITEv1 and PYBD

mpy-cross:
- do not automatically build mpy-cross, rather do it manually
- main: only accept full emit cmdline options if native enabled
- make mpconfigport.h compatible with msvc compiler
- add msvc build of mpy-cross
- set number of registers in nlr_buf_t based on native arch
- enable Xtensa-Windowed native emitter
- support armv7em, armv7emsp, armv7emdp architectures
- README.md: add notes about -march and -O

all ports:
- provide mp_hal_stdio_poll for sys.stdio polling where needed
- add new make target "submodules" which inits required modules

minimal port:
- use soft float for CROSS=1 Cortex-M4 target
- frozentest: recompile now that mpy version has changed
- set CSUPEROPT=-Os to get minimal firmware size

unix port:
- mpconfigport.mk: update comment about TLS implementations
- unix_mphal: use CLOCK_MONOTONIC for ticks_ms/us when available
- enable sys.atexit, triggered after the main script ends
- main: only accept full emit cmd-line options if native enabled
- coverage: add coverage tests for ringbuf
- convert to use FROZEN_MANIFEST to specify frozen code
- enable module weak links
- enable uos.VfsLfs1, uos.VfsLfs2 on coverage build
- modtermios: fix output speed setter in tcsetattr

windows port:
- mpconfigport.h: define empty MP_WEAK symbol
- mpconfigport.h: don't define restrict/inline/alignof for C++
- msvc: treat compiler warnings as errors
- Makefile: make use of CFLAGS_EXTRA, LDFLAGS_EXTRA and SRC_MOD
- msvc: remove unneeded definitions for qstr generation
- msvc: move build options from .vcxproj to .props files
- msvc: enable overriding directories used in the build
- msvc: change the way sources are listed
- default to binary mode for files
- enable module weak links

qemu-arm port:
- add testing of frozen native modules
- convert to use FROZEN_MANIFEST to specify frozen code
- add ldscript dependency in the final firmware.elf target
- let tinytest.o be built by standard build rules
- Makefile: allow overriding CROSS_COMPILE from another makefile

stm32 port:
- usb: refactor CDC VCP code to enable N CDC interfaces
- usb: support up to 3 VCP interfaces on USB device peripheral
- boards/make-pins.py: allow pins.csv to skip or hide board-pin name
- boards/pllvalues.py: search nested headers for HSx_VALUE defines
- boards: add board definition files for PYBD -SF2, -SF3, -SF6
- modpyb: add pyb.country() function to set the country
- extint: add extint_set() function for internal C access to EXTI
- mphalport: add support for having MAC in OTP region
- add low-level SDIO interface for cyw43 driver
- integrate in the cyw43 driver and network.WLAN class
- boards/PYBD_SFx: enable CYW43 WLAN driver
- modnetwork: replace generic netif NIC polling with specific code
- integrate optional mbedTLS component for ussl module
- boards/PYBD_SFx: enable ussl module using mbedTLS
- support optional lwIP mDNS responder
- lwip_inc: update to enable mDNS, TCP listen backlog, faster DHCP
- usbd_msc: rework USBD MSC code to support multiple logical units
- usbd_msc: provide custom irquiry processing by MSC interface
- usbd_msc: provide Mode Sense response data in MSC interface
- usb: use ARG_xxx enums to access kw args in pyb_usb_mode
- usb: add "msc" kw-arg to pyb.usb_mode to select MSC logical units
- usbd_msc: allow to compile when USB enabled and SD card disabled
- in link script, define start of stack separately from heap end
- boards: enable ussl module via mbedtls for boards with network
- Makefile: print info messages about use of mboot/QSPI flash
- enter bootloader via a system reset
- boards/pllvalues.py: support HSx_VALUE defined without uint32_t
- boards: add stm32??xx_hal_conf_base.h files with common settings
- boards: rework all stm32??xx_hal_conf.h files to use common code
- usb: fix regression with auto USB PID value giving PID=0xffff
- boards: optimise flash and RAM allocation for L4 boards
- mpu: add helper functions for configuring MPU
- eth: use MPU helper functions to configure MPU for ETH use
- sdram: use MPU helper functions to configure MPU for SDRAM use
- qspi: use MPU to allow access to valid memory-mapped QSPI region
- qspi: force a reset of the QSPI peripheral when initialising it
- qspi: handle bus acquisition
- powerctrl: add hooks for a board to perform actions on sleep/wake
- boards/PYBD_SFx: put SPI flash to sleep during sleep modes
- mpconfigport.h: enable useful networking modules if lwIP enabled
- usb: add support to auto-detect USB interface, either FS or HS
- usb: add "port" keyword argument to pyb.usb_mode, to select FS/HS
- spi: factor out code to calculate SPI source frequency
- extint: simplify bitband support config for different MCUs
- modmachine: make RTC class available in machine module
- boards/PYBD_SF2: put mbedtls library code in external QSPI flash
- update components to work with new H7xx HAL
- Makefile: remove Wno-attributes for ll_usb HAL file
- Makefile: use startup_stm32*.s file from stm32lib
- boards: remove startup_stm32*.s files now they are in stm32lib
- mpu: include MPU functions when ETH is enabled
- lwip_inc: define LWIP_NO_CTYPE_H=1 to use lwIP ctype funcs
- modmachine: disable IRQs before entering bootloader
- boards/PYBD_SFx: configure EN_3V3 pin as output on boot
- sdcard: add hook for a board to power on SD/MMC
- boards/PYBD_SFx: automatically turn on EN_3V3 when powering SD/MMC
- add initial support for STM32L0xx MCUs
- boards: add MCU support files for STM32L072
- mpconfigport.h: make "framebuf" module configurable by a board
- boards/NUCLEO_L073RZ: add definition files for new board
- powerctrl: move L0's SystemClock_Config to powerctrlboot.c file
- powerctrl: move F0's SystemClock_Config to powerctrlboot.c
- remove SystemInit funcs, use stm32lib versions instead
- boards/NUCLEO_F446RE: enable DAC
- add support for STM32L452 MCUs
- boards/NUCLEO_L452RE: add definition files for new board
- boards/NUCLEO_F413ZH: remove STARTUP_FILE, it's defined globally
- mboot: make _estack an array to avoid compiler warnings
- mboot: remove use of BSRRL/H for H7 MCUs due to stm32lib update
- mboot: use STARTUP_FILE from stm32lib
- mboot: update dependencies to enable parallel build with -j
- boards/B_L072Z_LRWAN1: add definition files for new board
- gccollect: always use MP_STATE_THREAD(stack_top) to get stack top
- usb: add config options to disable USB MSC and/or HID
- usbd_cdc_interface: make CDC TX/RX buffer sizes configurable
- add support for USB on L0 MCUs
- powerctrlboot: increase SYSCLK to 32MHz for L0 MCUs
- mphalport: fix GPIO clock enable for L0 MCUs
- Makefile: allow a board to disable float support
- boards/B_L072Z_LRWAN1: enable USB VCP support
- boards/STM32F769DISC: fix length of FLASH_APP section
- make-stmconst.py: allow more variation in parens and int-suffix L
- add initial support for STM32WBxx MCUs
- boards: add MCU support files for STM32WB55
- boards/NUCLEO_WB55: add definition files for new board
- boards/USBDONGLE_WB55: add definition files for new board
- flashbdev: support internal filesystem on STM32F722/23/32/33
- boards/stm32f722.ld: provide memory regions for internal FS
- boards/NUCLEO_F722ZE: add definition files for new board
- dma: fix re-start of DMA stream by clearing all event flags
- usbd_hid_interface: rewrite USB HID interface code
- boards/xxx_WB55: enable USB HID now that it works on WB MCUs
- usbd_hid_interface: include extra header to build with threading
- lwip_inc: enable raw socket type
- mpconfigport.h: enable lwIP raw sockets
- sdcard: support configuring the SD/MMC bus width to 1 or 4 bits
- modpyb: support building with PY_PYB_LEGACY on and HW_USB_HID off
- usbd: introduce MICROPY_HW_USB_IS_MULTI_OTG to simplify USB config
- usbd: support USB device mode on STM32L432 MCUs
- boards/NUCLEO_L432KC: add config for USB VCP support
- usbd: make USB device FIFO sizes dynamically configurable
- i2c: fix generation of restart condition for hw I2C on F0/F7
- mphalport: put PYBD specific MAC code in board specific file
- mboot/Makefile: define "BUILDING_MBOOT" when building mboot
- boards/PYBD_SF2: exclude certain things when building mboot
- extint: fix EXTI mapping of PVD and RTC events for H7 MCUs
- stm32_it: include correct EXTI interrupt handlers for L0 MCUs
- dma: fix DMA config for L0 MCUs
- powerctrl: fix machine.bootloader() for L0 MCUs
- machine_adc: add machine.ADC class
- machine_adc: improve operation of ADC for H7, L4 and WB MCUs
- boards/stm32wb55_af.csv: fix ADC pin-channel function mapping
- mboot: support boards with only two LEDs
- boards/NUCLEO_L073RZ: fix typo in MCU name
- boards/MIKROE_CLICKER2_STM32: add MikroElektronika Clicker2 board
- boards/STM32F769DISC: fix number of SDRAM row bits
- board/NUCLEO_F746ZG: enable Ethernet periph, lwip and ussl
- usb: add support for VCP+MSC+HID mode, incl 2xVCP and 3xVCP
- usb: verify number of used endpoints doesn't exceed maximum
- lwip_inc: allocate additional MEMP_SYS_TIMEOUT when mDNS enabled
- lwip_inc: enable LWIP_NETIF_EXT_STATUS_CALLBACK for mDNS
- machine_adc: fix build for F4 and L4 MCUs that only have ADC1
- modusocket: fix NULL deref when accept() an unbound socket
- machine_i2c: add ability to specify I2C(4) by name
- can: factor CAN driver into low-level and Python bindings
- add support for FDCAN peripheral, exposed as pyb.CAN
- boards/NUCLEO_H743ZI: enable FDCAN on this board
- use mp_printf with MICROPY_ERROR_PRINTER for uncaught exceptions
- can: guard header file by MICROPY_HW_ENABLE_CAN
- usbd_cdc_interface: add CTS flow control option for USB VCP
- support disabling the compiler
- powerctrlboot: fix clock and PLL selection for HSI48 on F0 MCUs
- powerctrlboot: add support for HSI at 8MHz on F0 MCUs
- uart: add RTS/CTS pin configuration support to UART4
- provide port-specific implementation for Nimble on STM32
- mpconfigport.h: add modbluetooth module to stm32
- boards/PYBD: enable BLE for Pyboard D
- system_stm32: support selection of HSE and LSI on L4 MCUs
- boards: enable MICROPY_HW_RTC_USE_LSE on L4 boards
- {adc,machine_adc}: change ADC clock and sampling time for F0 MCUs
- usbdev: fix compile error if MICROPY_HW_USB_CDC_NUM is set to 2
- boards/PYBD_SF2: put nimble library in external QSPI XIP flash
- extract port-specific Nimble implementation
- mboot: add option to automatically reset when USB is disconnected
- sdcard: support boards with no SD card detect pin
- use hardware double sqrt on F7/H7 MCUs
- boards: add new board ADAFRUIT_F405_EXPRESS
- convert to use FROZEN_MANIFEST to specify frozen code
- adc: update ADC driver to work with the new H7 HAL
- adc: remove unused macro and channel check, and fix spacing
- adc: use IS_CHANNEL_INTERNAL macro to check for internal channels
- adc: fix sampling for internal channels on H7 MCUs
- mpu: save and restore the IRQ state when configuring MPU
- accel: rename MMA I2C macro constants to make it generic
- accel: add support for KXTJ3
- boards: add NADHAT_PYB405 board
- accel: fix Accel.read() method so it does read a byte
- powerctrlboot: fix config of systick IRQ priority on F0/L0/WB MCU
- sdram: fix to use new mpu_config_start/mpu_config_end signature
- Makefile: only enable hardware sqrt on parts that support it
- timer: fix Timer.freq() calc so mult doesn't overflow uint32_t
- add soft timer implementation, using SysTick at 1ms resolution
- add machine.Timer with soft timer implementation
- add support for RF coprocessor on WB55 MCUs
- boards: enable support for bluetooth on WB55 boards
- mpthreadport: include runtime.h to get defn of mp_raise_msg
- boards/stm32f405_af.csv: fix typo in ETH_RMII_REF_CLK on PA1
- nimble_hci_uart.c: prevent scheduler running during CYW-BT wakeup
- generalise flash mounting code so it supports arbitrary FS
- storage: make pyb.Flash configurable, and support ext block proto
- main: auto detect block device used for main filesystem
- moduos: add VfsLfs1 and VfsLfs2 to uos module, if enabled
- boards: enable LFS2 on PYBv1.x and PYBD boards
- storage: change storage_read/write_blocks to return int type
- storage: make start/len args of pyb.Flash keyword only
- qstrdefsport.h: remove unused qstrs and make USB ones conditional
- boards/NUCLEO_L073RZ: skip board-pin names for CPU only pins
- main: fix auto creation of pyb.Flash on boot with kw-only args
- mpconfigport.h: use IRQ_PRI_PENDSV to protect bluetooth ringbuf
- uart: add support for UART4/5 on L0 MCUs
- boards/xxx_WB55: enable littlefs2 on WB55 boards
- main: fix SKIPSD file detection so SD card is mounted by default
- Makefile: enable max buffer size on W5200 NIC when used with lwIP
- modusocket: handle case of NULL NIC in socket ioctl
- boards/PYBD_SF2: configure LEDs as inverted, for LED.intensity()
- boards/NUCLEO_F767ZI: add pins and config for using an SD card
- boards/NUCLEO_F767ZI: update pins, peripherals and total flash
- boards/NUCLEO_H743ZI: add extra pins and peripheral definitions
- timer: add missing TIM 1/15/16/17 IRQ handlers for H7 MCUs
- boards/PYBD: include webrepl helper scripts in frozen manifest

esp8266 port:
- uart: fix invalid ringbuf name when event driven REPL enabled
- provide custom machine_time_pulse_us that feeds soft WDT
- mpconfigport.h: enable lwIP raw sockets
- machine_uart: allow remapping UART TX/RX pins from 1/3 to 15/13
- put new profile code in iROM
- machine_adc: rename pyb_adc_* to machine_adc_*
- machine_adc: add read_u16 method and refactor
- add per-board configs, following other ports
- modules/ntptime.py: always close socket, and set day-of-week
- convert to use FROZEN_MANIFEST to specify frozen code
- allow building without a manifest
- boards: add manifest_release.py with files for a release
- modules/flashbdev.py: support extended block protocol
- moduos: add optional support for VfsLfs1 and VfsLfs2

esp32 port:
- machine_timer: reuse Timer handles, deallocate only on soft-reset
- add machine.SDCard class using built-in HW SD/MMC controller
- update to use ESP IDF v3.3-beta3
- modnetwork: still try to reconnect to WLAN even with AUTH_FAIL
- Makefile: include all driver/*.c source files in the build
- network_ppp: add ppp_set_usepeerdns(pcb, 1) when init'ing iface
- add support for hardware I2C
- Makefile: fix path expansion for ESPIDF_DRIVER_O
- Makefile: put OBJ and LIB rule additions in gen_espidf_lib_rule
- Makefile: simplify include of IDF source by using wildcards
- pin MicroPython tasks to a specific core
- Makefile: include CFLAGS_EXTRA in CFLAGS definition
- network_ppp: add authentication support to the PPP interface
- add support for mDNS queries and responder
- modules: on initial setup mount internal flash at root
- add per-board configs, following other ports
- add esp32.Partition class to expose partition and OTA funcs
- add 'config' function to network.LAN, reusing network.WLAN
- Makefile: fix subst->patsubst in ESPIDF_BOOTLOADER_SUPPORT_O
- machine_adc: add ADC.read_u16() method
- update to use ESP IDF v3.3
- boards/TINYPICO: switch to use QIO and 80MHz for SPI interface
- add VFS FAT partition to partitions.csv and mount it as the FS
- add support for ESP32-D2WD with 2MiB internal flash
- modules/inisetup.py: use bdev.ioctl instead of bdev.SEC_SIZE
- Makefile: add SDKCONFIG_H to QSTR_GLOBAL_REQUIREMENTS
- support building with ESP IDF 4.0-beta1
- add check to Makefile for pyparsing version
- add check to Makefile that the toolchain is in PATH
- main: use both 3.3 and 4.0 config vars to enable SPIRAM
- Makefile: fix printing of supported git hash
- enable native emitter
- implement BLE using Nimble from IDF 4.x
- boards: enable BLE by default when building with IDF 4.x
- add 4.x version of IDLE WDT config
- run NimBLE on the app core
- convert to use FROZEN_MANIFEST to specify frozen code
- machine_uart: add ability to invert UART pins
- boards: split out CPU frequency config, make 160MHz the default
- machine_hw_spi: fix exception msg when host is already in use
- Makefile: add correct arch to MPY_CROSS_FLAGS for native code
- remove unused "esponewire.c" in favour of extmod/modonewire
- esp32_partition: support extended block protocol
- moduos: enable uos.VfsLfs2 for littlefs filesystems
- boards/sdkconfig.base: resize SSL output buffer from 16 to 4kiB
- rtc: set system microseconds when setting time via RTC.datetime()
- machine_rtc: make RTC.memory size and availability configurable
- machine_rtc: reduce memory footprint of user mem functionality
- boards: enable ULP in base sdk configuration
- boards/TINYPICO: add tinypico.py, dotstar.py with custom manifest
- esp32_rmt: add initial support for RMT peripheral

javascript port:
- enable support for frozen bytecode via FROZEN_MPY_DIR

nrf port:
- led: adjust how board LEDs are defined
- clean up source by removing tabs, trailing spaces, non-ASCII chars
- machine/adc: add ADC.read_u16() method
- add ADC channel mapping to alt function table
- machine/adc: allow to pass a Pin object in to ADC constructor
- machine/adc: fix mapping of ADC channel to pin
- boards/make-pins.py: fix gen of board pins to use correct index
- Makefile: add support for flashing with a Black Magic Probe
- boards: add Particle Xenon board configuration (an nRF52840)
- boards: add board definition for uBlox Nina B1 series BLE modules
- i2c: add support for TWIM (EasyDMA)
- temp: move module configuration guard
- uart: add support for UARTE (EasyDMA)
- flash: update flash driver to use nrfx_nvmc driver
- led: expose public API for LED manipulation
- main: update the way the LED is used on startup
- add support to activate MICROPY_PY_SYS_STDFILES
- device: correct SPIM3 IRQ handler entry for nrf52840
- add tinyusb support for nrf52840
- boards: add support for pca10059
- add nrf9160 base support
- boards: add nrf9160 pca10090 board
- main: execute boot.py/main.py frozen modules without a file system
- boards/particle_xenon: enable USB CDC on Particle Xenon board

powerpc port:
- add initial port to bare metal PowerPC arch

samd port:
- add new port to Microchip SAMDxx microcontrollers
- make common linker scripts, rename board.mk to mpconfigboard.mk
- boards: add Adafruit Feather M0 Express board configuration
- boards: add Mini SAM M4 board configuration
- add minimum config for Atmel SAMD21-XPLAINED-PRO board

zephyr port:
- main: use mp_stack API instead of local pointer for stack top

docs:
- machine: add initial docs for new machine.SDCard class
- library/framebuf: add missing module reference in example code
- library/sys: add documentation for sys.atexit function
- pyboard: update name of mounted volume to match code
- pyboard: clarify initial files on pyboard and fix up formatting
- library: document that sys.version_info returns a 3-tuple only
- pyboard: emphasize the instructions for making a USB mouse
- reference/speed_python: update that read-only buffers are accepted
- reference/speed_python: add missing self to var caching example
- library/pyb.DAC.rst: correct frequency for triangle mode output
- rename machine.ADC docs to machine.ADCWiPy
- library: specify new machine.ADC class
- library/pyb.rst: update docs for pyb.usb_mode() function
- library/pyb.rst: update pyb.usb_mode() to mention VCP+MSC+HID
- library/pyb.USB_VCP.rst: add info about id and flow params
- develop/qstr.rst: add documentation for string interning
- library/bluetooth: add initial BLE documentation
- reference/glossary.rst: add new terms and reduce complexity of old
- library/bluetooth.rst: clarify gap_advertise adv_data behavior
- library/bluetooth.rst: explain how to increase char buffer size
- library/bluetooth.rst: fix typo in HR/UART services example
- esp8266/tutorial: make http_get sample function self contained
- library: clarify relation between machine and port-specific mods
- esp8266: add ntptime usage to esp8266 quickref
- fix spelling in various parts of the docs
- wipy/tutorial: link Blynk examples to the official library
- library: rename "array" module to "uarray"
- library/bluetooth: rename to "ubluetooth"
- move ubluetooth under "MicroPython-specific libraries"
- library: add documentation for extended block device protocol
- library/ubluetooth: add docs for gatts_set_buffer
- conf.py: fix path to favicon.ico
- templates/topindex.html: replace usage of deprecated defindex.html
- library/machine.SDCard.rst: fix various typos
- library/ubluetooth: fix name and link to FLAG_xxx constants
- reference: add docs describing use of pyboard.py
- library: add docs for pyb.Flash class
- add littlefs docs and a filesystem tutorial
- reference/filesystem: fix typo in block device code example
- reference/filesystem: add note and example about using filesystem
- library/ubluetooth: add note about API being under development
- library/uos: add notes and links about littlefs failures
- library/uos.rst: clarify why the extended interface exists
- esp8266/quickref: add note that machine.RTC is not fully supported
- reference: add documentation describing use of .mpy files
- develop: add documentation on how to build native .mpy modules
- esp32: add quickref and full docs for esp32.RMT class

travis:
- build PYBD_SF2 board as part of the stm32 job
- selectively fetch git submodules only when needed
- build esp8266 firmware as part of Travis CI
- build esp32 firmware as part of Travis CI
- enable performance benchmark tests on standard unix build
- add samd port to Travis build
- build stm32 mboot for PYBD_SF6 as part of CI
- switch unix stackless build to use clang
- build an stm32 board with threading enabled to test it with CI
- add new job to test unix port with sys.settrace enabled
- add ESP32 build with IDF v4
- build more stm32 boards to cover all supported MCUs
- build unix nanbox with PYTHON=python2
- add BLE submodules to ESP32 IDF4 build
- add esp8266 GENERIC_512K build to CI
- use "make submodules" to init required modules for each port
- add job to build and test unix minimal port
- add tests for building and importing dynamic native modules
- build urandom native module in coverage job

examples:
- bluetooth: add basic BLE peripheral examples
- bluetooth: use UUIDs directly to add services to adv payload
- bluetooth/ble_uart_peripheral.py: add usage demo
- embedding: replace symlink of mpconfigport.h with real file
- bluetooth/ble_uart_peripheral: use append mode for RX char
- embedding: remove obsolete fatfs files from build
- bluetooth: add helpers for decoding advertising payloads
- bluetooth: add example for reading temperature sensor
- natmod: add btree example
- natmod: add uheapq example
- natmod: add uzlib example
- natmod: add framebuf example
- natmod: add ure example
- natmod: add features1 and features2 examples
- natmod: add urandom native module example
- network: add testing key/cert to SSL HTTP server example
- natmod: add very simple features0 example to compute factorial

miscellaneous:
- top: add CODEOFCONDUCT.md document based on the PSF code of conduct
- gitignore: put build-*/ pattern in top-level gitignore file
- gitattributes: mark *.a files as binary

Improved mpy format with support for native code, and new JavaScript …

…port

In this release the mpy file format has been moved to version 4 and has
some significant improvements: mpy file size is reduced on average by about
35%, loading time of mpy files is reduced by about 40%, and they now have
support to save native, viper and inline assembler code (or machine code
generated from any other source).  Size reduction of mpy files was achieved
by adding a qstr window to reuse past qstrs when encoding them, by packing
qstrs directly in the bytecode, and by defining a static qstr set.

Some VM opcodes were also changed to fix a bug when doing a break/continue
out of a finally block, and to make some simplifications.  In particular
POP_BLOCK and POP_EXCEPT opcodes were replaced with POP_EXCEPT_JUMP.

Most uppercase macros have been converted to lowercase to make a more
consistent C API, including all MP_OBJ_IS_xxx and MP_xxx_SLOT_IS_FILLED
macros.

The default PYTHON makefile variable is now changed from "python" to
"python3", but Python 2 is still supported via "make PYTHON=python2".

The mpy-cross compiler supports the new mpy version 4 and has new command
line options: "-march=<arch>" to select the native emitter, and "--version"
to print the MicroPython version and the mpy version.  Also mpy-tool.py has
support for freezing native code.

A module system for external, user C modules has been implemented and
documentation for this is available in the new "docs/develop" section.

A new "javascript" port has been added which targets JavaScript as the
machine via Emscripten.  This allows to run MicroPython as an application
within node.js, and to run it within a browser (among other things).

All bare-metal ports have the following improvements: machine.sleep() is
now machine.lightsleep(), and both lightsleep() and deepsleep() now take an
optional argument which is the maximum time to sleep in milliseconds.
These ports also now allow freezing of boot.py and main.py using the usual
methods.  And a new I2C method i2c.writevto(addr, vect) is added which can
be used to write a tuple/list of buffers all at once to an I2C device.

The stm32 port now has a fully integrated Ethernet MAC driver (see the
network.LAN class) using lwIP for the TCP/IP stack, and sockets were made
significantly more robust.  Support for F413 MCUs was added.  There are
also some minor user-facing changes to this port:
- machine.UART (and pyb.UART) now defaults to timeout=0 (was 1000ms) which
  gives UARTs a non-blocking behaviour.
- The USB REPL is now configurable using uos.dupterm, and by default
  pyb.USB_VCP(0) is put on dupterm slot 1 before boot.py is executed.  To
  disable the default REPL use: uos.dupterm(None, 1).
- pyb.DAC(id) will now only reset the DAC the first time it is called; to
  get the old behaviour pass the bits parameter like: pyb.DAC(id, bits).
- pyb.DAC.noise() and pyb.DAC.triangle() now output at full scale.
- The system will not recreate boot.py if it's missing (it will only create
  it if the filesystem is corrupt, or when doing a factory reset).

For the esp32 port, the build process has been updated to align better with
the ESP IDF and now uses sdkconfig to configure features.  Dual core mode
is now enabled by default, SPIRAM is in memory-mapped mode so all of it can
be used for the MicroPython heap, there is support to change the CPU
frequency, and the WDT now panics and resets the device if it times out.

A detailed list of changes follows.

py core:
- remove calls to file reader functions when these are disabled
- add optional support for 2-argument version of built-in next()
- compile: swap order of pop_block/pop_except in "except as" handler
- warning: support categories for warnings
- builtinhelp: only print help re FS modules if external import enabled
- downcase all MP_OBJ_IS_xxx macros to make a more consistent C API
- downcase MP_xxx_SLOT_IS_FILLED inline functions
- mkenv.mk: change default PYTHON variable from "python" to "python3"
- qstr: evaluate find_qstr only once then pass to Q_GET_HASH macro
- obj.h: remove obsolete mp_obj_new_fun_viper() declaration
- objfun: make fun_data arg of mp_obj_new_fun_asm() a const pointer
- eliminate warnings about unused arguments when debugging disabled
- compile: fix handling of unwinding BaseException in async with
- compile: add optimisation to compile OrderedDict inplace
- objexcept: fix hash of exc str created in mp_obj_new_exception_msg
- py.mk: update lwip build config to work with latest lwip version
- fix VM crash with unwinding jump out of a finally block
- vm: remove currently_in_except_block variable
- replace POP_BLOCK and POP_EXCEPT opcodes with POP_EXCEPT_JUMP
- persistentcode: add a qstr window to save mpy files more efficiently
- persistentcode: pack qstrs directly in bytecode to reduce mpy size
- persistentcode: define static qstr set to reduce size of mpy files
- add independent config for debugging sentinel object values
- emitnative: consolidate where HASCONSTS is set to load-const-obj fun
- emitnative: provide concentrated points of qstr emit
- emitnative: adjust accounting of size of const_table
- emitglue: remove union in mp_raw_code_t to combine bytecode & native
- add support to save native, viper and asm code to .mpy files
- persistentcode: bump .mpy version to 4
- allow registration of modules at their definition
- implement a module system for external, user C modules
- update and rework build system for including external C modules
- move mp_native_type_from_qstr() from emitnative.c to nativeglue.c
- nativeglue: rename native convert funs to match other native helpers
- compile: add support to select the native emitter at runtime
- compile: support multiple inline asm emitters
- compile: check that arch is set when compiling native, viper or asm
- runtime: remove long-obsolete MICROPY_FSUSERMOUNT init code
- scheduler: convert micropythyon.schedule() to a circular buffer
- nlrthumb: add support for iOS where the C func is _nlr_push_tail
- makedefs: use io.open with utf-8 encoding when processing source
- runtime: optimise to not create temp float for int to power negative
- runtime: fix mp_unpack_ex so seq can't be reclaimed by GC during use
- mpprint: support printing %ld and %lu formats on 64-bit archs
- asmthumb: support asm_thumb code running on normal ARM processors
- native: improve support for bool type in viper functions
- remove "if (0)" and "if (false)" branches
- objgenerator: fix handling of None passed as 2nd arg to throw()
- objgenerator: remove unneeded forward decl and clean up white space
- misc.h: rename _MP_STRINGIFY to not use leading underscore in ident
- persistentcode: change "len" type to size_t for mp_obj_str_get_data
- objarray: add support for memoryview.itemsize attribute
- objarray: add decode method to bytearray
- update makefiles to use $(CAT) variable instead of hard coded "cat"
- update makefiles to use $(TOUCH) instead of hard coded "touch"

extmod:
- moduzlib: update to uzlib 2.9.2
- modlwip: add support for polling UDP sockets for writability
- moduhashlib: include implementation of sha256 only when required
- convert legacy uppercase macro names to lowercase
- moduwebsocket: refactor `websocket` to `uwebsocket`
- modlwip: change #ifdef to #if for check of MICROPY_PY_LWIP
- modlwip: fix bug when polling listening socket with backlog=1
- modlwip: add concurrency protection macros
- modwebrepl: fix logic to handle a put of file of size 0
- vfs_fat: update for new oofatfs version
- modlwip: fix case where concurrency lock isn't released on error
- moduselect: adjust select_select and poll_register to use size_t
- vfs_fat: fallback to FAT32 if standard FAT16/SFD format fails
- modlwip: handle case of connection closing while on accept queue
- modlwip: handle case of accept callback called with null PCB
- modlwip: protect socket.accept with lwIP concurrency lock
- modlwip: free any stored incoming bufs/connections on TCP error
- modlwip: use correct listening socket object in accept callback
- modlwip: abort TCP conns that didn't close cleanly in a while
- modurandom: add init method to seed the Yasmarang generator
- machine_signal: fix fault when no args are passed to Signal()
- modussl_mbedtls: support non-blocking handshake
- modussl_axtls: add non-blocking mode support
- moducryptolib: add optional AES-CTR support
- modujson: handle parsing of floats with + in the exponent
- machine_i2c: change C-level API to allow split I2C transactions
- machine_i2c: remove need for temporary memory in writemem() call
- machine_i2c: add i2c.writevto() that can write a vector of bufs
- modlwip: free any incoming bufs/connections before closing PCB
- modlwip: register TCP close-timeout callback before closing PCB

lib:
- utils/pyexec: implement paste mode with event driven REPL
- utils/printf: exclude __GI_vsnprintf alias for gcc 9 and above
- utils/gchelper_m3: add license header and clean up code
- utils/gchelper_m3: add gc_helper_get_sp() function
- utils/gchelper: add gchelper.h header file for assembler functions
- netutils: add function to print tracing info for Ethernet frames
- oofatfs: update oofatfs library to R0.13c working branch
- oofatfs: update ffconf.h config for new oofatfs version
- oofatfs: update oofatfs library to fix issue with logic not
- stm32lib: update library to fix F7 MMC capacity calculation
- utils/pyexec: add pyexec_file_if_exists() helper function
- utils: make pyexec_file_if_exists run frozen scripts if they exist
- utils/interrupt_char: invalidate interrupt char at start up
- stm32lib: update library to fix UART9/10 baudrate on F4 MCUs
- nrfx: upgrade nrfx to v1.7.1 plus a UART bug fix

drivers:
- memory/spiflash: rework wait_sr to fix uninit'd variable 'sr'
- display/ssd1306.py: change to use new i2c.writevto() method

tools:
- mpy-tool.py: add support for freezing native code
- upip.py: use "raise arg" instead of no-arg raise form, for native
- pyboard.py: add missing line from example usage comments
- mpy-tool.py: adjust use of super() to make it work with Python 2
- mpy-tool.py: fix init of QStrWindow, and remove unused variable
- pyboard.py: don't accumulate output data if data_consumer used
- upip.py: add support for multiple index URLs with custom default

tests:
- basics: add tests for try-except-else and try-except-else-finally
- run-tests: support running native tests via mpy
- import: add test for importing x64 native code
- extmod: add test for FAT filesystem on a very large block device
- run-tests: ignore exception in process kill when ending repl test
- micropython: add some tests for failed heap allocation
- skip tests needing machine module if (u)machine doesn't exist
- ussl_basic: disable setblocking() calls
- basics/sys1.py: add test for calling sys.exit() without any args
- pyb: update UART expected output now that default timeout is 0
- basics: add coverage tests for memoryview attributes

mpy-cross:
- enable building of x64 native .mpy files
- add "-march=<arch>" option to select native emitter
- support compiling with MICROPY_PY___FILE__ enabled
- automatically select ARMV6 arch when running on such a host
- add --version command line option to print version info

all ports:
- change PYB message prefix to MPY
- convert legacy uppercase macro names to lowercase
- update to work with new oofatfs version
- {stm32,esp8266}: set mpy-cross native arch for frozen native code
- convert to use pyexec_file_if_exists() to execute boot/main.py

unix port:
- mpthreadport: add thread deinit code to stop threads on exit
- mpthreadport: cleanup used memory on thread exit
- mpthreadport: remove busy wait loop in thread garbage collection
- modmachine: handle repeated /dev/mem open errors
- modffi: eliminate unused-argument warning when debugging disabled
- Makefile: update coverage tests to match those in Travis
- mpthreadport: use named semaphores on Mac OS X
- gcollect: make sure stack/regs get captured properly for GC
- coverage: add test for printing literal % character
- modusocket: fix use of setsockopt in usocket.settimeout impl
- modusocket: raise ETIMEDOUT when connect or accept has timeout

windows port:
- fix line wrapping behaviour on the REPL

qemu-arm port:
- rework to run bare-metal on boards with Cortex-M CPUs
- use gchelper code to get registers for GC scanning

stm32 port:
- implement machine.lightsleep()
- rtc: check RTCEN=1 when testing if RTC is already running on boot
- usbdev: add USB config option for board being self powered
- usbdev: add USB config option for max power drawn by the board
- main: make board-defined UART REPL use a static object and buffer
- boards/stm32f429_af.csv: fix typos in UART defs Tx->TX and Rx->RX
- mboot: add option to autodetect the USB port that DFU uses
- sdcard: don't use SD clock bypass on F7 MCUs
- usb: add flow control option for USB VCP data received from host
- boards/make-pins.py: add basic support for STM32H7 ADC periphs
- boards/stm32h743_af.csv: add ADC entries to pin capability table
- adc: add basic support for ADC on a pin on STM32H7 MCUs
- mboot: use USB HS as main USB device regardless of USB_HS_IN_FS
- mboot: add support for STM32F769 MCUs
- mboot: add support for GPIO ports G, H, I and J
- mboot: allow deploying via deploy-stlink
- usb: use USB HS as main USB device regardless of USB_HS_IN_FS
- usbd_conf: fully support USB HS with external PHY
- modmachine: make bootloader() enter custom loader if it's enabled
- boards/STM32F769DISC: support the use of USB HS with external PHY
- boards/STM32F769DISC: configure for use with mboot by default
- systick: rename sys_tick_XXX functions to systick_XXX
- systick: make periodic systick callbacks use a cyclic func table
- pendsv: clean up pendsv IRQ handler and eliminate duplicate code
- pendsv: add ability to schedule callbacks at pendsv IRQ level
- systick: provide better compile-time configurability of slots
- modnetwork: change lwIP polling to be based on background systick
- move gchelper assembler code to lib/utils for use by other ports
- gccollect: use gchelper.h header instead of explicit declaration
- pendsv: fix inline asm constant and prefix with # character
- mboot/Makefile: support specifying BOARD_DIR for custom board
- boards/NUCLEO_L476RG: add support for RNG, DAC and CAN1
- boards/make-pins.py: add cmdline options to support use by mboot
- mboot/Makefile: generate all pin header files from board pins.csv
- mboot/mphalport.h: include genhdr/pins.h for access to pin names
- qspi: use static af functions for pin configuration
- mboot: add support for loading gzip'd firmware from a filesystem
- mboot: move some BSS vars to new section that isn't zeroed out
- mboot: add support script which can program mboot and application
- modmachine: add ability to pass through user data to mboot
- mboot: add hook to run board-specific code early on startup
- boards/stm32f429.ld: increase uPy heap size by 64k for F429 MCU
- extint: fix ExtInt to work with non-GPIO pins
- extint: fix RTC Alarm/FS USB EXTI constants for L4
- make-stmconst.py: improve regex to parse more constants
- extint: add non-GPIO EXTI IRQ sources for F0
- extint: remove unused (and incorrect) EXTI defines
- stm32_it: fix RTC IRQ handler to handle all EXTI IRQs on F0 MCUs
- sdram: increase GPIO speed for SDRAM interface to "very high"
- boards/NUCLEO_F767ZI: fix up comments about HCLK computation
- mphalport: add mp_hal_get_mac() helper function
- eth: add low-level Ethernet MAC driver
- network_lan: add high-level network.LAN interface to ETH driver
- mpconfigport.h: enable lwIP concurrency protection mechanism
- modnetwork: don't call NIC callback if it's NULL
- boards/NUCLEO_F767ZI: enable lwIP and Ethernet peripheral
- boards/STM32F7DISC: enable lwIP and Ethernet peripheral
- boards/STM32F769DISC: enable lwIP and Ethernet peripheral
- boards/NUCLEO_F429ZI: enable lwIP and Ethernet peripheral
- qspi: enable sample shift and disable timeout counter
- Makefile: allow a board to specify its linker sections for FW
- boards/STM32F769DISC: use external QSPI flash to store some code
- use global lwip build config and support building without lwip
- boards: update to use new build config for lwip component
- add compile-time option to use HSI as clock source
- mboot: update to match latest oofatfs version
- allow to build with threading with the GIL disabled
- qspi: set pin speed to very-high and allow to config some options
- usb: allow to override USB strings & VID/PID in app and mboot
- stm32_it: guard UART7_IRQHandler with check for UART7 define
- mboot: set USE_MBOOT=1 by default in the Makefile
- system_stm32: provide default value for HSI calibration
- mpconfigport.h: remove malloc/free/realloc helper macros
- boards/STM32L476DISC: enable servo support on STM32L476DISC board
- Makefile: allow to override CROSS_COMPILE with included Makefile
- make default USB_VCP stream go through uos.dupterm for main REPL
- timer: expose the PWM BRK capability of Timer 1 and 8
- uart: handle correctly the char overrun case of RXNE=0 and ORE=1
- rename MICROPY_HW_HAS_SDCARD to MICROPY_HW_ENABLE_SDCARD
- add support for MMC driver, exposed via pyb.MMCard class
- moduos: allow to compile again without USB enabled
- network_wiznet5k: add ability to trace Ethernet TX and RX frames
- network_wiznet5k: add ability to set the MAC address
- network_wiznet5k: automatically set MAC if device doesn't have one
- i2cslave: add support for H7 MCUs
- usbd_conf: add support for USB HS peripheral on H7 MCUs
- mboot: add support for H7 MCUs, with H743 flash layout
- boards/NUCLEO_H743ZI: add config options to support mboot
- boards/NUCLEO_L432KC: disable complex nos and default frozen mods
- rtc: add auto-LSE-bypass detection with fallback to LSE then LSI
- rtc: remove unused LSE detection code
- rtc: remove non-ASCII mu-character from source code comment
- timer: correctly initialise extended break settings on F7/H7/L4
- system_stm32f0: enable PWR clock on startup
- system_stm32f0: add support for using HSE and PLL as SYSCLK
- powerctrl: enable EIWUP to ensure RTC wakes device from standby
- dac: rework DAC driver to use direct register access
- usbdev: make USB device descriptors at runtime rather than static
- usb: add USB device mode for VCP+VCP without MSC
- powerctrl: deselect PLLSAI as 48MHz src before turning off PLLSAI
- usb: remove mp_hal_set_interrupt_char now that it's reset at boot
- main: increase default UART REPL rx buffer from 64 to 260 bytes
- powerctrl: support changing frequency when HSI is clock source
- flash: fix bug computing page number for L432 page erase
- add support for F413 MCUs
- boards: add NUCLEO_F413ZH board configuration
- machine_uart: change default UART timeout to 0, for non blocking
- move factory reset files and code to separate source file
- usbd_cdc_interface: don't retransmit chars if USB is reconnected
- rtc: allow overriding startup timeouts from mpconfigboard
- dma: initialise all members of DMA structs for H7 MCUs
- dma: always reset and configure the H7 DMA peripheral
- spi: enable SPI IRQs and add IRQHandlers for H7 MCUs
- irq: fix IRQ_ENABLE_STATS stats config to work on all MCUs
- boards/NUCLEO_H743ZI: enable SPI3 on this board
- modmachine: create dedicated asm function to branch to bootloader
- adc: fix VBAT_DIV to be 4 for STM32F411
- machine_i2c: update to support new C-level I2C API
- i2c: make timeout for hardware I2C configurable
- machine_i2c: simplify ROM initialisation of static HW I2C objects
- i2c: support setting the I2C TIMINGR value via keyword arg
- sdcard: add switch break to ensure only correct SD/MMC IRQ is run
- sdram: update MPU settings to block invalid region, change attrs
- mboot/README: fix some typos, describe bootloader and fwupdate.py
- modmachine: in bootloader() disable caches before reset of periphs

cc3200 port:
- mods/modussl: fix ca_certs arg validation in mod_ssl_wrap_socket
- modmachine: rename machine.sleep to machine.lightsleep
- use common gchelper_m3.s code from lib/utils
- mpconfigport.h: disable compiler optimisation of OrderedDict

esp8266 port:
- modmachine: implement optional time_ms arg to machine.deepsleep
- modmachine: rename machine.sleep to machine.lightsleep
- modmachine: implement simple machine.lightsleep function
- modmachine: in lightsleep, only waiti if wifi is turned off
- modmachine: call ets_event_poll after waiti in machine.idle
- modmachine: handle overflow of timer to get longer periods
- fix ticks_ms to correctly handle wraparound of system counter

esp32 port:
- don't put py/scheduler.o in iRAM, it's no longer needed
- Makefile: put all IDF compenents in .a libs to use IDF ld script
- update to latest ESP IDF using sdkconfig and new ldgen procedure
- machine_timer: deinit all active timers on soft reset
- Makefile: make sure that directory exists for sdkconfig.h
- boards: use auto xtal freq config instead of default 40MHz
- modsocket: fix crashes when connect/bind can't resolve given addr
- modmachine: rename machine.sleep to machine.lightsleep
- use SPIRAM in mem-map mode so all of it can be used for uPy heap
- modmachine: add support for changing the CPU frequency
- modsocket: fix usocket.send to accept anything with buffer proto
- modsocket: change socket.socket to be socket type rather than fun
- network_lan: add arg to constructor to set clock mode for ETH PHY
- modnetwork: catch and report Ethernet events
- network_lan: make power arg to constructor optional
- modnetwork: fix wifi.isconnected to return False after disconnect
- modnetwork: implement RSSI for WiFi STA via WLAN.status('rssi')
- modnetwork: remove redundant esp_log include
- Makefile: add some missing IDF source files to bootloader and app
- mphalport: use ets_delay_us for mp_hal_delay_us_fast
- machine_pin: make it so None as pull value disables pull up/down
- machine_pin: add new PULL_HOLD pin pull mode
- machine_pin: rework pull mode config to fix GPIO hold feature
- mpthreadport: exit vPortCleanUpTCB early if threading not init'd
- boards: enable dual core support by default
- boards/sdkconfig: disable WDT check of idle task on CPU1
- README: add info about pyparsing and the correct Python version
- machine_wdt: add timeout arg to select interval, make WDT panic
- modnetwork: change type to size_t for uses of mp_obj_str_get_data
- machine_uart: implement UART.deinit() method
- network_ppp: add a timeout for closing PPP connection
- machine_touchpad: use HW timer for FSM to enable wake-on-touch
- modsocket: raise EAGAIN when accept fails in non-blocking mode

javascript port:
- add new port targeting JavaScript via Emscripten
- fix Emscripten async load, and to compile with modern clang
- library: use Buffer.alloc() since new Buffer() is deprecated
- pass (error) exit value out from script to process caller
- Makefile: fix unrepresentable float error by using clamp
- library: print data as raw bytes to stdout so unicode works

nrf port:
- modmachine: rename machine.sleep to machine.lightsleep
- uart: use formula instead of switch for baudrate calculation
- uart: remove unused machine.UART() parameters
- shrink "<peripheral> does not exist" error messages
- pin: cleanup Pin.__str__ to print relevant information
- pin: print pull information in Pin.__str__
- ticker: remove duplicate NRFX_IRQ_PRIORITY_SET
- timer: fix disabling Timer 1 when using soft PWM
- readme: update link to nrfjprog download
- bluetooth: improve advertisment behavior for nrf52 targets
- bluetooth: resolve compilation warning in ble_drv.c
- readme: update make flash command when defining board
- pwm: remove superfluous NULL in machine_hard_pwm_instances
- bluetooth: add support for SoftDevice s132 version 6.1.1
- board: migrate all nrf52832 targets to new BLE stack
- bluetooth: deprecate use of SoftDevice s132 v6.0.0
- bluetooth: add support for SoftDevice s140 version 6.1.1
- board: migrate nrf52840 target to new BLE stack
- bluetooth: deprecate use of SoftDevice s140 v6.0.0
- readme: add section about LTO
- Makefile: update to match latest oofatfs version
- boards: add support for BLYST Nano module based boards
- change types to size_t for all uses of mp_obj_str_get_data
- machine/i2c: update to support new C-level I2C API
- nrfx_glue: adapt to nrfx v.1.7.1
- uart: change UART driver to be non-blocking and use IRQs
- mpconfigport.h: enable MICROPY_KBD_EXCEPTION by default
- uart: make UART print output something, and add write method
- mphalport: use wfi to save power while waiting at the UART REPL

zephyr port:
- modzephyr: revamp stacks_analyze() call
- modzsensor: rename "TEMP" sensor channel to "DIE_TEMP"
- prj_minimal.conf: switch to CONFIG_STDOUT_CONSOLE
- Makefile: proxy ram_report, rom_report targets from Zephyr
- prj_frdm_k64f.conf: add fxos8700 sensor
- prj_frdm_kw41z.conf: add new board configuration
- i2c: add support for hardware i2c
- CMakeLists.txt: set AR to point to the Zephyr toolchain exe
- machine_i2c: update to support new C-level I2C API
- switch back to enabling I2C in board-specific configs

docs:
- machine: change sleep to lightsleep and add timeout arguments
- convert all cases of machine.sleep to machine.lightsleep
- ure: fix match.group signature to indicate index param is required
- uos: document extra requirements on stream objs passed to dupterm
- pyboard: add link to pyboard v1.1 schematic and layout PDF
- pyboard: make pyboard v1.1 pinout the default shown in quickref
- develop: fix typos in C-module example for example_add_ints
- library/machine.Pin: add PULL_HOLD constant to possible pin pulls
- esp32: add a note to quickref about use of Pin.PULL_HOLD
- esp32: add example for pin isolation in combination with deepsleep
- develop: remove paragraph that was copied in error from other doc
- cmodules: fix example to globally define MODULE_EXAMPLE_ENABLED
- cmodules: note the various ways MODULE_EXAMPLE_ENABLED can be set
- esp8266: add tutorial for APA102 LEDs
- esp32: correct quickref for ESP32 hardware SPI with non-default IO
- machine.I2C: add writevto method to write a vector of byte bufs
- pyboard/quickref: refer to new machine.I2C instead of old pyb.I2C

travis:
- update to use Ubuntu 16.04 Xenial for CI builds
- enable test for running native code via mpy

Vast improvements to native emitter, new nrf port, unified documentation

In this release there are a wide range of improvements and additions to
both the core and the ports.  In the core the main improvement was to the
native emitter to have much more comprehensive support for general Python
features, such as generators and complex exception handling, and the
generated machine code is smaller and retains its efficiency.  Elsewhere,
fuzzy testing was used to find and eliminate some corner-case bugs, user
classes were optimised when they don't use special accessors, underscores
in numeric literals are now supported (PEP515), and the uio.IOBase class
was added to allow user defined streams.

For the extended modules there is now a VfsPosix filesystem component,
a new ucryptolib module with AES support, addition of ure.sub() and of
uhashlib.md5, and the lwIP socket implementation now has working TCP
listen/accept backlog.

Compared to the last release the minimal baseline core code size is reduced
by about 2.2%, down by roughly 1500 bytes for bare-arm port and 3500 bytes
for minimal x86 port.  Most other ports have increased in size due to the
addition of new features (eg ucryptolib, ure.sub).

The stm32 port sees the introduction of a new bootloader -- mboot -- which
supports DFU upload via USB FS, USB HS, as well as a custom I2C protocol,
and also support to program external SPI flash.  There is significant
refactoring of the USB device driver, improved VCP throughput, and support
for 2x VCP interfaces on the one USB device.  lwIP has been integrated, and
support added for SDRAM.  Cortex-M0 CPUs are now supported along with
STM32F0 MCUs.

For the esp8266 port the heap is increased by 2kbytes, the radio is
automatically put to sleep if no WLAN interfaces are active, and the UART
can now be disconnected from the REPL and its RX buffer length configured.
Upon soft-reset sockets are now cleaned up.

The esp32 port has added support for external SPI RAM, PPPoS functionality,
improved performance and stability when using threads, and other general
bug fixes.

There is a new nrf port for Nordic MCUs, currently supporting nRF51x and
nRF52x chips.

The docs have now been unified so there is just one set of documentation
covering all ports.  And initial documentation for the esp32 port is added.

There are two changes at the Python API level that are not backwards with
previous versions:
- uos.dupterm now requires that a stream passed to it is derived from
  uio.IOBase (or is a native stream object).
- The esp32 neopixel driver has had its default timing changed from 400kHz
  to 800kHz; existing code that didn't explicitly specify the "timing"
  parameter in the NeoPixel constructor may need to be updated to specify
  this as "timing=0" to get 400kHz timing.

A detailed list of changes follows.

py core:
- mpconfig.h: be stricter when autodetecting machine endianness
- mpstate.h: adjust start of root pointer section to exclude non-ptrs
- nlrx86: use naked attribute on nlr_push for gcc 8.0 and higher
- vm: adjust #if logic for gil_divisor so braces are balanced
- objfun: fix variable name in DECODE_CODESTATE_SIZE() macro
- vm: use enum names instead of magic numbers in multi-opcode dispatch
- vm: improve performance of opcode dispatch when using switch stmt
- repl: fix handling of unmatched brackets and unfinished quotes
- misc.h: add MP_STATIC_ASSERT macro to do static assertions
- compile: change comment about ITER_BUF_NSLOTS to a static assertion
- emitbc: avoid undefined behavior calling memset() with NULL 1st arg
- parsenum: use int instead of mp_int_t for parsing float exponent
- parsenum: avoid undefined behavior parsing floats with large exponents
- objfloat: fix undefined shifting behavior in high-quality float hash
- mpz: avoid undefined behavior at integer overflow in mpz_hash
- objfloat: fix undefined integer behavior hashing negative zero
- gc: when GC threshold is hit don't unnecessarily collect twice
- parsenum: adjust braces so they are balanced
- modbuiltins: add support for rounding integers
- objgenerator: save state in old_globals instead of local variable
- objgenerator: protect against reentering a generator
- emit: combine fast and deref into one function for load/store/delete
- emit: combine yield value and yield-from emit funcs into one
- emit: combine build tuple/list/map emit funcs into one
- emit: combine name and global into one func for load/store/delete
- emit: combine load/store/delete subscr into one emit function
- emit: combine load/store/delete attr into one emit function
- emit: combine break_loop and continue_loop into one emit function
- emit: combine import from/name/star into one emit function
- emit: merge build set/slice into existing build emit function
- emit: combine setup with/except/finally into one emit function
- objtype: fix assertion failures in mp_obj_new_type by checking types
- objtype: fix assertion failures in super_attr by checking type
- stream: move definition of mp_stream_p_t from obj.h to stream.h
- reader: allow MICROPY_VFS_POSIX to work with MICROPY_READER_POSIX
- mpconfig.h: add default MICROPY_VFS_FAT config value
- obj.h: introduce a "flags" entry in mp_obj_type_t
- objtype: don't expose mp_obj_instance_attr()
- objtype: optimise instance get/set/del by skipping special accessors
- gc: add gc_sweep_all() function to run all remaining finalisers
- lexer: add support for underscores in numeric literals
- modio: add uio.IOBase class to allow to define user streams
- mkrules.mk: regenerate all qstrs when config files change
- stream: introduce and use efficient mp_get_stream to access stream_p
- objarray: replace 0x80 with new MP_OBJ_ARRAY_TYPECODE_FLAG_RW macro
- add checks for stream objects in print() and sys.print_exception()
- compile: combine break and continue compile functions
- compile: combine subscript_2 and subscript_3 into one function
- compile: combine global and nonlocal statement compile functions
- compile: combine or_test and and_test compile functions
- compile: combine expr, xor_expr and and_expr into one function
- compile: handle return/break/continue correctly in async with
- objgenerator: eliminate need for mp_obj_gen_wrap wrapper instances
- obj.h: fix broken build for object repr C when float disabled
- simplify some cases of accessing the map of module and type dict
- objdict: make mp_obj_dict_get_map an inline function
- objmodule: make mp_obj_module_get_globals an inline function
- obj.h: give compile error if using obj repr D with single-prec float
- malloc: give a compile warning if using finaliser without GC
- objgenerator: implement __name__ with normal fun attr accessor code
- emitnative: optimise for iteration asm code for non-debug build
- runtime: use mp_obj_new_int_from_ll when return int is not small
- stream: introduce MP_STREAM_GET_FILENO ioctl request
- objstr: in format error message, use common string with %s for type
- asmthumb: optimise native code calling runtime glue functions
- mpconfig.h: introduce MICROPY_DEBUG_PRINTER for debugging output
- fix compiling with debug enabled and make more use of DEBUG_printf
- emitnative: factor common code for native jump helper
- emitnative: fix x86 native zero checks by comparing full word
- asmx86: use generic emit function to simplify cmp emit function
- emitnative: fix native locals stack to start at correct location
- emitnative: simplify handling of exception objects from nlr_buf_t
- emitnative: allocate space for local stack info as it's needed
- compile: for dynamic compiler, widen literal 1 to get correct shift
- py.mk: don't hardcode path to libaxtls.a
- gc: in gc_alloc, reset n_free var right before search for free mem
- objarray: allow to build again when bytearray is disabled
- stream: adjust mp_stream_posix_XXX to take void*, not mp_obj_t
- emitnative: use small tables to simplify handling of local regs
- asmxtensa: handle function entry/exit when stack use larger than 127
- asm*: support assembling code to jump to a register, and get PC+off
- emitnative: optimise and improve exception handling in native code
- asmxtensa: fix bug with order of regs in addi encoding
- asmxtensa: optimise loading local addr and support larger offsets
- emitnative: fix bug with store of 16 and 32 values in viper ARM mode
- asmxtensa: use narrow version of add instr to reduce native code size
- emitnx86: fix number of args passed to mp_setup_code_state, 4 not 5
- vm: fix handling of finally-return with complex nested finallys
- emitnative: cancel caught exception once handled to prevent reraise
- emitnative: add support for return/break/continue in try and with
- compile: factor code that compiles start/end of exception handler
- py.mk: build axtls library directly from its source files
- runtime: fix incorrect test for MICROPY_PORT_DEINIT_FUNC
- objarray: bytearray: allow 2nd/3rd arg to constructor
- emitnative: fix try-finally in outer scope, so finally is cancelled
- fix native functions so they run with their correct globals context
- optimise call to mp_arg_check_num by compressing fun signature
- asmx64: fix bug in assembler when creating disp with r13 and 0 offset
- {asmx86,asmx64}: extend test_r8_with_r8 to accept all 8 lower regs
- emit: move MP_EMIT_OPT_xxx enums from compile.h to emitglue.h
- emit: remove need to call set_native_type to set native/viper mode
- emit: remove need to call set_native_type to set viper return type
- emit: completely remove set_native_type, arg type is set in compiler
- compile: merge viper annotation and normal param compilation stages
- compile: factor code that compiles viper type annotations
- emitnative: reuse mp_native_type_from_qstr when searching for a cast
- make viper functions have the same entry signature as native
- emitnative: support arbitrary number of arguments to viper functions
- emitnative: use macros instead of raw offsetof for slot locations
- emitnative: make viper funcs run with their correct globals context
- asmxtensa: make indirect calls using func table, not raw pointers
- asmthumb: detect presence of I-cache using CMSIS macro
- objtype: clarify comment about configuring inplace op methods
- shorten error messages by using contractions and some rewording
- objstr: make % (__mod__) formatting operator configurable
- modbuiltins: make oct/hex work when !MICROPY_PY_BUILTINS_STR_OP_MODULO
- objgenerator: implement PEP479, StopIteration convs to RuntimeError
- parsenum: avoid rounding errors with negative powers-of-10
- modmath: add math.factorial, optimised and non-opt implementations
- objstr: format: return bytes result for bytes format string
- fix msvc C++ compiler warnings with MP_OBJ_FUN_MAKE_SIG macro
- vm: make small optimisation of BUILD_SLICE opcode
- objfloat: fix abs(-0.0) so it returns 0.0
- emitnative: place const objs for native code in separate const table
- asm*: remove ASM_MOV_REG_ALIGNED_IMM emit macro, it's no longer used
- emitnative: change type of const_table from uintptr_t to mp_uint_t
- vm: fix case of throwing GeneratorExit type into yield-from
- runtime: remove nlr protection when calling __next__ in mp_resume
- objtype: support full object model for get/set/delitem special meths
- vm: when VM raises exception put exc obj at beginning of func state
- asmthumb: add wide ldr to handle larger offsets
- asmthumb: clean up asm_thumb_bl_ind to use new optimised ldr helper
- asmthumb: extend asm entry/exit to handle stack larger than 508 bytes
- asmx86: comment out unused asm_x86_nop to prevent compiler warnings
- asmx64: extend asm_x64_mov_reg_pcrel to accept high registers
- asmxtensa: use proper calculation for const table offset
- emitnative: reorder native state on C stack so nlr_buf_t is first
- emitnative: implement yield and yield-from in native emitter
- runtime: use mp_import_name to implement tail of mp_import_from
- runtime: remove comment in mp_import_name about level being 0
- obj.h: use uint64_t instead of mp_int_t in repr-D MP_OBJ_IS_x macros
- emitnative: clean up unused macro and forward function declarations
- asmx64: change stack management to reference locals by rsp not rbp
- asmx64: change indirect calls to load fun ptr from the native table
- asmx86: change stack management to reference locals by esp not ebp
- asmx86: change indirect calls to load fun ptr from the native table
- emitnative: load native fun table ptr from const table for all archs
- asmarm: simplify asm_arm_bl_ind to only load via index, not literal
- asmthumb: remove unused fun_ptr arg from asm_thumb_bl_ind function
- emitnative: remove unused ptr argument from ASM_CALL_IND macro
- emitnative: consolidate use of stacked immediate values to one func
- emitnative: simplify viper mode handling in emit_native_import_name
- emitnative: push internal None rather than const obj where possible
- emitnative: put None/False/True in global native const table
- objtype: remove comment about catching exc from user __getattr__
- objstr: make str.count() method configurable
- objmodule: implement PEP 562's __getattr__ for modules
- py.mk: when building axtls use -Wno-all to prevent all warnings
- compile: fix case of eager implicit conversion of local to nonlocal
- compile: remove unneeded variable from global/nonlocal stmt helpers
- scope: optimise scope_find_or_add_id to not need "added" arg
- runtime: fix qstr assumptions when handling "import *"
- unicode: fix check for valid utf8 being stricter about contn chars
- py.mk: fix broken Gmane URL
- add option to reduce GC stack integer size to save RAM
- objboundmeth: support loading generic attrs from the method
- obj: add support for __int__ special method
- objexcept: use macros to make offsets in emergency exc buf clearer
- objexcept: make sure mp_obj_new_exception_msg doesn't copy/format msg
- objdict: make .fromkeys() method configurable
- bc: fix calculation of opcode size for opcodes with map caching
- qstr: put a lower bound on new qstr pool allocation
- objarray: introduce "memview_offset" alias for "free" field of object
- gc: adjust gc_alloc() signature to be able to accept multiple flags
- mpconfig: move MICROPY_VERSION macros to static ones in mpconfig.h
- runtime: unlock the GIL in mp_deinit function
- get optional VM stack overflow check compiling and working again
- fix location of VM returned exception in invalid opcode and comments
- modio: make iobase_singleton object const so it goes in ROM
- obj.h: explicitly cast args to uint32_t in MP_OBJ_FUN_MAKE_SIG

extmod:
- modlwip: update to work with lwIP v2.0
- modlwip: set POLLHUP flag for sockets that are new
- modlwip: allow to compile with MICROPY_PY_LWIP disabled
- modussl_mbedtls: populate sock member right away in wrap_socket
- modussl_mbedtls: use mbedtls_entropy_func for CTR-DRBG entropy
- vfs: use u_rom_obj properly in argument structures
- vfs_fat: rename FileIO/TextIO types to mp_type_vfs_fat_XXX
- add VfsPosix filesystem component
- vfs: add fast path for stating VfsPosix filesystem
- vfs: introduce a C-level VFS protocol, with fast import_stat
- moduhashlib: prefix all Python methods and objects with uhashlib
- moduhashlib: reorder funcs so that they are grouped by hash type
- moduhashlib: allow to disable the sha256 class
- moduhashlib: allow using the sha256 implementation of mbedTLS
- moduhashlib: make function objects STATIC
- uos_dupterm: use native C stream methods on dupterm object
- modussl_axtls: fix __del__ to point to mp_stream_close_obj
- vfs_fat_diskio: factor disk ioctl code to reduce code size
- update to use new mp_get_stream helper
- moducryptolib: add ucryptolib module with crypto functions
- moducryptolib: optionally export MODE_* constants to Python
- moducryptolib: refactor functions for clean interface with axTLS
- moducryptolib: add an mbedTLS implementation for this module
- moducryptolib: prefix all Python methods/objects with ucryptolib
- moducryptolib: shorten exception messages to reduce code size
- moducryptolib: don't include arpa/inet.h, it's not needed
- modure: add match.groups() method, and tests
- modure: add match.span(), start() and end() methods, and tests
- modure: add ure.sub() function and method, and tests
- vfs: support opening a file descriptor (int) with VfsPosix
- fix to support compiling with object representation D
- vfs_posix: support ilistdir with no (or empty) argument
- vfs_posix: use DTTOIF if available to convert type in ilistdir
- modlwip: deregister all lwIP callbacks when closing a socket
- modussl: support polling in ussl objects by passing through ioctl
- modbtree: update to work with new mp_stream_posix_XXX signatures
- modussl_axtls: use MP_ROM_PTR for objects in allowed args array
- moduhashlib: add md5 implementation, using axTLS
- moduhashlib: use newer message digest API for mbedtls >=2.7.0
- moduhashlib: add md5 implementation using mbedtls
- moductypes: remove BITFIELD from aggregate types enum
- moductypes: accept OrderedDict as a structure description
- modonewire: fix reset timings to match 1-wire specs
- moductypes: make sizeof() accept "layout" parameter
- modlwip: implement TCP listen/accept backlog
- modlwip: fix read-polling of listening socket with a backlog
- moductypes: implement __int__ for PTR
- moductypes: add aliases for native C types

lib:
- lwip: update lwIP to v2.0.3, tag STABLE-2_0_3_RELEASE
- stm32lib: update library to include support for STM32F0 MCUs
- utils/printf: make DEBUG_printf implementation more accessible
- utils: fix to support compiling with object representation D
- utils: expose pyb_set_repl_info function public
- libm_dbl/tanh: make tanh more efficient and handle large numbers
- libm/math: make tanhf more efficient and handle large numbers
- libm/wf_tgamma: fix tgammaf handling of -inf, should return nan
- libm_dbl: add implementation of copysign() for DEBUG builds
- stm32lib: update library to fix issue with filling USB TX FIFO
- libm/math: fix int type in float union, uint64_t should be uint32_t
- libm/math: add implementation of __signbitf, if needed by a port
- utils/pyexec: forcefully unlock the heap if locked and REPL active
- utils: add generic MicroPython IRQ helper functions
- stm32lib: update library to get F413 BOR defs and fix gcc 8 warning

drivers:
- wiznet5k: fix bug with MACRAW socket calculating packet size
- memory/spiflash: move cache buffer to user-provided config
- memory/spiflash: rename functions to indicate they use cache
- memory/spiflash: add functions for direct erase/read/write
- sdcard: change driver to use new block-device protocol
- sdcard: fix bug in computing number of sectors on SD Card
- sdcard: do not release CS during the middle of read operations
- cc3000: use cc3000_time_t instead of time_t for custom typedef
- display/lcd160cr.py: in fast_spi, send command before flushing
- sdcard: in test use os.umount and machine module instead of pyb
- sdcard: remove debugging print statement in ioctl method
- dht: allow open-drain-high call to be DHT specific if needed

tools:
- pydfu.py: increase download packet size to full 2048 bytes
- pydfu.py: add support for multiple memory segments
- pydfu.py: use getfullargspec instead of getargspec for newer pyusb
- pydfu.py: workaround stdio flush error on Windows with Python 3.6
- pydfu.py: improve DFU reset, and auto-detect USB transfer size
- mpy-tool.py: support freezing of floats in obj representation D
- mpy-tool.py: put frozen bignum digit data in ROM, not in RAM
- mpy-tool.py: set sane initial dynamic qstr pool size with frozen mods
- mpy-tool.py: fix calc of opcode size for opcodes with map caching
- mpy-tool.py: fix build error when no qstrs present in frozen mpy
- dfu.py: pad image data to 8 byte alignment to support L476
- pyboard.py: run exec: command as a string
- pyboard.py: change base class of PyboardError to Exception
- pyboard.py: in TelnetToSerial.close replace try/except with if

tests:
- basics/special_methods2: enable some additional tests that work
- add some tests for bigint hash, float hash and float parsing
- extmod: add test for importing a script from a user VFS
- extmod: remove conditional import of uos_vfs, it no longer exists
- pyb: make i2c and pyb1 pyboard tests run again
- io: add simple IOBase test
- extmod: add test for VFS and user-defined filesystem and files
- unix/extra_coverage: don't test stream objs with NULL write fun
- extmod/ujson_dump.py: add test for dump to non-stream object
- extmod: add test for ujson.dump writing to a user IOBase object
- import: add test for importing invalid .mpy file
- add tests using "file" argument in print and sys.print_exception
- extmod/ucryptolib*: add tests for ucryptolib module
- extmod/ucryptolib*: add into and inplace tests for ucryptolib
- basics/namedtuple*: import ucollections first
- move non-filesystem io tests to basics dir with io_ prefix
- improve feature detection for VFS
- run-tests: add nrf target
- run-tests: improve crash reporting when running on remote targets
- extmod/ujson_dump_iobase.py: return number of bytes written
- make tests work on targets without float support
- micropython/viper_cond: add test for large int as bool
- run-tests: enable bool1.py test with native emitter
- micropython: add tests for try and with blocks under native/viper
- basics/set_pop.py: sort set before printing for consistent output
- basics/int_big_error.py: use bytearray to test for int overflow
- modify tests that print repr of an exception with 1 arg
- basics: provide .exp files for generator tests that fail PEP479
- run-tests: enable native tests for unwinding jumps
- basics: add more tests for return within try-finally
- basics: add test cases for context manager raising in enter/exit
- float/cmath_fun.py: fix truncation of small real part of complex
- float: test -inf and some larger values for special math funcs
- remove pyboard.py symlink and instead import from ../tools
- extmod/uhashlib_md5: add coverage tests for MD5 algorithm
- float/float_parse.py: add tests for accuracy of small decimals
- cpydiff: add case for difference in behaviour of bytes.format()
- micropython: test loading const objs in native and viper funcs
- basics: split out gen throw tests from yield-from-throw tests
- run-tests: enabled native tests that pass now that yield works
- unix/ffi_float: skip if strtof() is not available
- uselect_poll_basic: add basic test for uselect.poll invariants
- uctypes_sizeof_od: test for using OrderedDict as struct descriptor
- basics/class_getattr: remove invalid test for __getattribute__
- make bytes/str.count() tests skippable
- extmod/uctypes_sizeof_layout: test for sizeof of different layout
- import: add .exp file for module_getattr.py to not require Py 3.7
- cmdline/cmd_showbc.py: fix test to explicitly declare nonlocal
- extmod: skip uselect test when CPython doesn't have poll()
- import_long_dyn: test for "import *" of a long dynamic name
- io: update tests to use uos.remove() instead of uos.unlink()
- basics/special_methods: add testcases for __int__
- extmod/uctypes_ptr_le: test int() operation on a pointer field
- extmod/uctypes_error: add test for unsupported unary op
- run-tests: make .exp and .out file names unique by prefixing with dir

mpy-cross:
- make build independent of extmod directory
- Makefile: also undefine MICROPY_FORCE_32BIT and CROSS_COMPILE

minimal port:
- main: allow to compile without GC enabled

unix port:
- support MICROPY_VFS_POSIX and enable it in coverage build
- moduos_vfs: add missing uos functions from traditional uos module
- mpconfigport.h: enable MICROPY_PY_UCRYPTOLIB
- mpconfigport_coverage: enable ure groups, span, start, end and sub
- modos: convert dir-type to stat-type for file type in ilistdir
- use MP_STREAM_GET_FILENO to allow uselect to poll general objects
- Makefile: coverage: Explicitly build "axtls" too
- Makefile: enable ussl module with nanbox build
- Makefile: remove building of libaxtls.a which is no longer needed
- Makefile: build libffi inside $BUILD
- mpconfigport_coverage.h: enable uhashlib.md5
- modos: include extmod/vfs.h for MP_S_IFDIR, etc
- modjni: update .getiter signature to include mp_obj_iter_buf_t*
- modjni: get building under coverage and nanbox builds
- mpconfigport.h: enable MICROPY_PY_UHASHLIB_MD5 for uhashlib.md5
- moduselect: raise OSError(ENOENT) if obj to modify is not in poller
- modusocket: initial implementation of socket.settimeout()
- modusocket: finish socket.settimeout() implementation
- modffi: add support for "q"/"Q" specs (int64_t/uint64_t)
- Makefile: allow to override/omit pthread lib name
- modos: rename unlink to remove to be consistent with other ports
- enable MICROPY_PY_BUILTINS_ROUND_INT
- enable uio.IOBase
- call gc_sweep_all() when doing a soft reset

windows port:
- make printing of debugging info work out of the box
- msvc: support custom compiler for header generation
- msvc: implement file/directory type query
- remove remaining traces of old GNU readline support

stm32 port:
- usbd_conf.h: remove unused macros and clean up header file
- usbd_conf: changes files to unix line endings and apply styling
- usbdev: convert files to unix line endings
- usbdev: remove unused RxState variable, and unused struct
- usbdev: be honest about data not being written to HID endpoint
- usbd_hid_interface: address possible race condition vs. interrupt
- i2c: add new hardware I2C driver for F4 MCUs
- machine_i2c: use new F4 hardware I2C driver for machine.I2C class
- accel: switch pyb.Accel to use new C-level I2C API
- modpyb: introduce MICROPY_PY_PYB_LEGACY config option for pyb mod
- pyb_i2c: put pyb.I2C under MICROPY_PY_PYB_LEGACY setting
- modpyb: remove unused includes and clean up comments
- usb: use usbd_cdc_itf_t pointer directly in USB_VCP class
- usb: combine CDC lower-layer and interface state into one struct
- usb: combine HID lower-layer and interface state into one struct
- usb: make CDC endpoint definitions private to core usbdev driver
- usb: change CDC tx/rx funcs to take CDC state, not usbdev state
- usb: change HID report funcs to take HID state, not usbdev state
- usb: add ability to have 2x VCP interfaces on the one USB device
- usb: initialise cdc variable to prevent compiler warnings
- enable UART7/8 on F4 series that have these peripherals
- add support for STM32L496 MCU
- boards: add board ld and af.csv files for STM32L496 MCU
- boards: add config files for new board, STM32L496GDISC
- rtc: don't try to set SubSeconds value on RTC
- integrate lwIP as implementation of usocket module
- rng: use Yasmarang for rng_get() if MCU doesn't have HW RNG
- remove unneeded HTML release notes from usbdev and usbhost dirs
- add low-level hardware I2C slave driver
- add new component, the mboot bootloader
- allow to have no storage support if there are no block devices
- add support for Cortex-M0 CPUs
- timer: make timer_get_source_freq more efficient by using regs
- allow a board to disable MICROPY_VFS_FAT
- boards: add startup_stm32f0.s for STM32F0 MCUs
- add support for STM32F0 MCUs
- boards: add alt-func CSV list and linker script for STM32F091
- boards: add NUCLEO_F091RC board configuration files
- README: update to include STM32F0 in list of supported MCUs
- boards: split combined alt-func labels and fix some other errors
- boards: ensure USB OTG power is off for NUCLEO_F767ZI
- flash: increase H7 flash size to full 2MiB
- modnetwork: don't take netif's down when network is deinited
- modnetwork: change base entry of NIC object from type to base
- modnetwork: provide generic implementation of ifconfig method
- add network driver for Wiznet5k using MACRAW mode and lwIP
- modnetwork: fix arg indexing in generic ifconfig method
- mpconfigport.h: enable DELATTR_SETATTR and BUILTINS_NOTIMPLEMENTED
- mboot: increase USB rx_buf and DFU buf sizes to full 2048 bytes
- Makefile: rebuild all qstrs when any board configuration changes
- boards/STM32L476DISC: update SPI flash config for cache change
- timer: support TIM1 on F0 MCUs
- i2c: fix num_acks calculation in i2c_write for F0 and F7 MCU's
- i2cslave: fix ordering of event callbacks in slave IRQ handler
- mboot: adjust user-reset-mode timeout so it ends with mode=1
- boards/stm32f091_af.csv: split labels that are multiple funcs
- boards/NUCLEO_F091RC: add Arduino-named pins and rename CPU pins
- can: use MP_OBJ_ARRAY_TYPECODE_FLAG_RW where appropriate
- spi: fix SPI driver so it can send/recv more than 65535 bytes
- mboot: define constants for reset mode cycling and timeout
- boards/NUCLEO_F091RC: fix TICK_INT_PRIORITY so it is highest prio
- qspi: don't require data reads and writes to be a multiple of 4
- mboot: add support for erase/read/write of external SPI flash
- boards: add .ld and af.csv files for STM32F722
- modnetwork: fix query of DNS IP address in ifconfig()
- mboot: fix bug with invalid memory access of USB state
- mboot: only compile in code for the USB periph that is being used
- mboot: always use a flash latency of 1WS to match 48MHz HCLK
- access dict map directly instead of using helper function
- support compiling with object representation D
- fatfs_port: fix bug when MICROPY_HW_ENABLE_RTC not enabled
- timer: use enum for indexing keyword arg in pyb_timer_init_helper
- timer: add tick_hz arg to Timer constructor and init method
- mphalport: make mp_hal_stdin_rx_chr/stdout_tx_strn weakly linked
- flashbdev: fix bug with L4 block cache, dereferencing block size
- add method for statically configuring pin alternate function
- sdcard: use mp_hal_pin_config_alt_static to configure SD card pins
- sdram: add SDRAM driver from OpenMV project
- sdram: integrate SDRAM driver into rest of code
- sdram: on F7 MCUs enable MPU on external SDRAM
- boards/STM32F429DISC: enable onboard SDRAM
- sdcard: get SDMMC alt func macro names working with F4,F7,H7 MCUs
- Makefile: use -Wno-attributes for ll_usb.c HAL source file
- rtc: get rtc.wakeup working on F0 MCUs
- modmachine: get machine.sleep working on F0 MCUs
- extint.h: use correct EXTI lines for RTC interrupts
- modmachine: get machine.sleep working on L4 MCUs
- adc: disable VBAT in read channel helper function
- adc: fix ADC reading on F0 MCUs to only sample a single channel
- spi: round up prescaler calc to never exceed requested baudrate
- sdram: allow additional config by a board, and tune MPU settings
- boards/STM32F429DISC: add burst len and autorefresh to SDRAM cfg
- boards/STM32F7DISC: enable onboard SDRAM
- spi: split out pyb.SPI and machine.SPI bindings to their own files
- spi: add implementation of low-level SPI protocol
- mboot/main: use correct formula for DFU download address
- Makefile: allow external BOARD_DIR directory to be specified
- boards/STM32L476DISC: enable external RTC xtal to get RTC working
- for MCUs that have PLLSAI allow to set SYSCLK at 2MHz increments
- dma: pass DMA direction as parameter to dma_init not in cfg struct
- dma: reinitialise the DMA if the direction changed on the channel
- sdcard: use only a single DMA stream for both SDIO TX/RX
- sdcard: move temporary DMA state from BSS to stack
- spi: be sure to set all SPI config values in SPI proto init
- change flash IRQ priority from 2 to 6 to prevent preemption
- flashbdev: protect flash writes from cache flushing and USB MSC
- sdcard: fully reset SDMMC periph before calling HAL DMA functions
- dma: get DMA working on F0 MCUs
- sdram: add support for 32-bit wide data bus and 256MB in MPU cfg
- boards/STM32F769DISC: add optional support for external SDRAM
- add support for STM32F765xx MCUs
- Makefile: include copysign.c in double precision float builds
- adc: fix ADC calibration scale for L4 MCUs, they use 3.0V
- adc: increase sample time for internal sensors on L4 MCUs
- dcmi: add F4/F7/H7 hal files and dma definitions for DCMI periph
- uart: add support for USART3-8 on F0 MCUs
- boards/NUCLEO_F091RC: enable USART3-8 with default pins
- modmachine: re-enable PLLSAI[1] after waking from stop mode
- powerctrl: move function to set SYSCLK into new powerctrl file
- powerctrl: fix configuring APB1/APB2 frequency when AHB also set
- powerctrl: factor code to set RCC PLL and use it in startup
- powerctrl: factor code that configures PLLSAI on F7 MCUs
- powerctrl: optimise passing of default values to set_sysclk
- powerctrl: don't configure clocks if already at desired frequency
- usbd_conf: allocate enough space in USB HS TX FIFO for CDC packet
- mpconfigport.h: enable math.factorial, optimised version
- main: add configuration macros for board to set heap start/end
- usbd_cdc_interface: handle disconnect IRQ to set VCP disconnected
- usbd_cdc_interface: refactor USB CDC tx code to not use SOF IRQ
- spi: fix calculation of SPI clock source on H7 MCUs
- boards/stm32h743.ld: fix total flash size, should be 2048k
- system_stm32: introduce configuration defines for PLL3 settings
- adc: add ADC auto-calibration for L4 MCUs
- flashbdev: add missing include for irq.h
- servo: only initialise TIM5 if it is needed, to save power
- usb: fully deinitialise USB periph when it is deactivated
- powerctrl: move (deep)sleep funcs from modmachine.c to powerctrl.c
- powerctrl: disable IRQs during stop mode to allow reconfig on wake
- boards/STM32F429DISC: enable UART as secondary REPL
- uart: always show the flow setting when printing a UART object
- mboot: provide led_state_all function to reduce code size
- mboot: add support for 4th board LED
- boards: add configuration for putting mboot on PYBv1.x
- mboot: add documentation for using mboot on PYBv1.x
- powerctrl: add support for standby mode on L4 MCUs
- uart: add rxbuf keyword arg to UART constructor and init method
- boards: add STM32L432KC chip configuration files
- add peripheral support for STM32L432
- boards: add NUCLEO_L432KC board configuration files
- split out UART Python bindings from uart.c to machine_uart.c
- uart: factor out code from machine_uart.c that computes baudrate
- uart: rework uart_get_baudrate so it doesn't need a UART handle
- uart: factor out code to set RX buffer to function uart_set_rxbuf
- uart: remove HAL's UART_HandleTypeDef from UART object struct
- uart: simplify deinit of UART, no need to call HAL
- uart: for UART init, pass in params directly, not via HAL struct
- uart: move config of char_width/char_mask to uart.c
- uart: add ability to have a static built-in UART object
- extint: use correct EXTI channels on H7 MCUs for RTC events
- adc: fix calibrated volt/temp readings on H7 by using 16bit scale
- adc: increase ADC sampling time for internal sources on H7 MCUs
- adc: support 16-bit ADC configuration on H7 MCUs
- boards: allow OpenOCD stm_flash procedure to accept single FW img
- boards/NUCLEO_L432KC: specify L4 OpenOCD config file for this MCU
- main: add board config option to enable/disable mounting SD card
- implement UART.irq() method with initial support for RX idle IRQ
- uart: fix uart_rx_any in case of no buffer to return 0 or 1
- uart: always enable global UART IRQ handler on init
- uart: clear overrun error flag after reading RX data register
- uart: make sure user IRQs are handled even with a keyboard intr
- modmachine: fix reset_cause to correctly give DEEPSLEEP on L4 MCU
- sdcard: properly reset SD periph when SDMMC2 is used on H7 MCUs
- wdt: make singleton WDT object const so it goes in ROM
- main: make thread and FS state static and exclude when not needed
- use MICROPY_GC_STACK_ENTRY_TYPE to save some RAM
- .gitattributes: remove special text handling of stm32 usbdev files
- enable MICROPY_PY_BUILTINS_ROUND_INT
- enable descriptors
- enable uio.IOBase
- enable ure.sub()
- call gc_sweep_all() when doing a soft reset

cc3200 port:
- mods: include stream.h to get definition of mp_stream_p_t
- mods: access dict map directly instead of using helper func
- use MICROPY_GC_STACK_ENTRY_TYPE to save some RAM

esp8266 port:
- mpconfigport.h: add some weak links to common Python modules
- modnetwork: return empty str for hostname if STA is inactive
- modnetwork: raise ValueError when getting invalid WLAN id
- modmachine: allow I2C and SPI to be configured out of the build
- change UART(0) to attach to REPL via uos.dupterm interface
- modules/ntptime.py: remove print of newly-set time
- mpconfigport.h: enable ucryptolib module for standard build
- esp8266_common.ld: put mp_keyboard_interrupt in iRAM
- modesp: run ets_loop_iter before/after doing flash erase/write
- let machine.WDT trigger the software WDT if obj is not fed
- Makefile: remove build of libaxtls.a and add back tuned config
- main: increase heap by 2kb, now that axtls rodata is in ROM
- remove scanning of GC pointers in native code block
- ets_alt_task: process idle callback if no other events occurred
- modnetwork: automatically do radio sleep if no interface active
- modnetwork: wait for iface to go down before forcing power mgmt
- machine_uart: add rxbuf keyword arg to UART constructor/init
- main: activate UART(0) on dupterm for REPL before boot.py runs
- esp_mphal: provide mp_hal_pin_od_high_dht so DHT works reliably
- implement high-res timers using new tick_hz argument
- use MICROPY_GC_STACK_ENTRY_TYPE to save some RAM
- enable MICROPY_PY_BUILTINS_ROUND_INT
- enable descriptors
- enable uio.IOBase
- enable ure.sub()
- call gc_sweep_all() when doing a soft reset, cleans up sockets

esp32 port:
- update to latest ESP IDF version
- modnetwork: fix STA/AP activate/deactivate for new IDF API
- Makefile: update to latest ESP IDF version
- esp32.custom_common.ld: put soc code in iram0
- silence ESP-IDF log messages when in raw REPL mode
- Makefile: extract common C & C++ flags for consistent compilation
- add support for building with external SPI RAM
- modnetwork: fix isconnected() when using static IP config
- remove port-specific uhashlib implementation and use common one
- fatfs_port: implement get_fattime so FAT files have a timestamp
- update to latest ESP IDF
- modules: include umqtt library in frozen modules
- mpconfigport.h: enable ucryptolib module
- allow to build with uPy floats disabled
- reduce latency for handling of scheduled Python callbacks
- modnetwork: add support for bssid parameter in WLAN.connect()
- implement WLAN.status() return codes
- modesp32: add raw temperature reading to esp32 module
- modesp32: use MP_ROM_QSTR and MP_ROM_PTR in const locals dict
- modnetwork: add network.(W)LAN.ifconfig('dhcp') support
- update to latest ESP IDF
- fix int overflow in machine.sleep/deepsleep functions
- machine_rtc: fix locals dict entry, init qstr points to init meth
- modesp32: add hall_sensor() function
- network_ppp: add PPPoS functionality
- mpthreadport: prevent deadlocks when deleting all threads
- allocate task TCB and stack from system heap not uPy heap
- machine_uart: add txbuf/rxbuf keyword args to UART construct/init
- machine_uart: implement UART.sendbreak() method
- machine_pwm: support higher PWM freq by auto-scaling timer res
- machine_pwm: on deinit stop routing PWM signal to the pin
- modmachine: enable machine.sleep() now that the IDF supports it
- mphalport: when tx'ing to REPL only release GIL if many chars sent
- modsocket: for socket read only release GIL if socket would block
- machine_pin: add Pin.off() and Pin.on() methods
- Makefile: use system provided math library rather than uPy one
- modules/neopixel.py: change NeoPixel to different default timings
- machine_hw_spi: use separate DMA channels for HSPI and VSPI
- machine_hw_spi: make HW SPI objects statically allocated
- implement high-res timers using new tick_hz argument
- enable MICROPY_PY_BUILTINS_ROUND_INT
- enable descriptors
- enable uio.IOBase
- enable ure.sub()
- call gc_sweep_all() when doing a soft reset

nrf port:
- add new port to Nordic nRF5x MCUs
- align help.c builtin help text to use correct type
- add WT51822-S4AT board
- use --gc-sections to reduce code size
- add compile switch to disable VFS
- enable Link-time optimizations (LTO)
- boards/arduino_primo: add missing hal_rng config used by random mod
- implement NVMC HAL
- disable FAT/VFS by default
- hal/nvmc: remove pre-compiler error thrown in nvmc.h, if on nrf52
- hal/hal_nvmc: fix non-SD code
- boards: update linker scripts
- add micro:bit filesystem
- drivers/bluetooth/ble_drv: don't handle non-events
- modules/uos/microbitfs: make OSError numeric
- main: run boot.py and main.py on startup
- use micropython libm to save flash
- main: add ampy support
- drivers/bluetooth: start advertising after disconnect
- update usage of mp_obj_new_str by removing last parameter
- remove default FROZEN_MPY_DIR
- option to enable Ctrl-C in NUS console
- boards/microbit: add copy of microbit display and image files
- boards/microbit: add copy of microbit font type from microbit-dal
- boards/microbit: rename display/image files from .cpp to .c ext
- boards/microbit: update board modules from C++ to C-code
- boards/microbit: add framework updates to build micro:bit modules
- boards/microbit: attempt to get working display/images without FP
- boards/microbit: add modmicrobit.h to expose module init function
- boards/microbit: include modmicrobit.h in board_modules.h
- drivers/softpwm: rename init function to softpwm_init0
- drivers/ticker: rework ticker functions for microbit display/music
- boards/microbit: update to work with new ticker code
- modules/music: remove init of softpwm/ticker upon music module load
- update main.c to init relevant board drivers, if enabled
- boards/microbit: move microbit target to custom linker script
- boards/microbit/modules: fix tabbing in modmicrobit.c
- boards/microbit: add temperature back to microbit module
- boards/microbit: update docs on top level tick low pri callback
- change board module header from board_modules.h to boardmodules.h
- add if-def around inclusion of nrf_sdm.h in main
- boards/microbit: enable music, display, image, microbit module
- drivers/bluetooth: reset evt_len to size of static buffer each iter
- add support for s132 v5.0.0 bluetooth stack (micropython#139)
- change PYB prefix to MPY
- only search for frozen files if FROZEN_MPY_DIR is set
- mpconfigport: reduce GC stack size for nrf51
- modules/machine/pin: disable pin debug by default
- boards/common.ld: avoid overflowing the .text region
- drivers/ble_drv: fixing sd_ble_enable bug for SD s132 v.2.0.1
- make machine.UART optional
- fix stack size in ld script and enable MICROPY_STACK_CHECK
- improve include of boardmodules.mk
- make LTO configurable via Makefile flag
- boards/microbit/modules: initialize variable in microbit_sleep
- replace custom-HAL with nrfx-HAL
- fix NUS console when using boot.py or main.py
- Makefile: fix .PHONY target
- enable -g flag by default
- make linker scripts more modular
- remove port member from Pin object
- modules/machine/pin: add support for IRQ on Pin's
- modules/machine/spi: sPIM (EasyDMA) backend for nrf52x
- drivers/bluetooth/ble_drv: increase max transfers in progress
- gccollect: use the SP register instead of MSP
- boards: remove unused defines from board config headers
- boards/wt51822_s4at: fixes after nrfx and Pin IRQ introduction
- modules/random: rename port config for RNG
- modules: align method to resolve pin object
- adc: allow for external use of new and value read function
- spi: allow for external use of new and transfer function
- return immediatly from mp_hal_delay_us if 0us is given
- modules/machine/adc: fix to make adc.c compile for nrf51 targets
- bluetooth: fixes for s132 v5 BLE stack
- Makefile: use "standard" GCC -fshort-enums instead of --short-enums
- Makefile: remove -fstack-usage
- Makefile: use C11 instead of Gnu99
- Makefile: refine dead-code elimination parameters
- modules/machine/adc: don't compare -1 to an unsigned number
- modules/uos/microbitfs: fix errno defines
- modules/uos/microbitfs: remove unused uos_mbfs_mount
- enable micro:bit FS by default
- boards/feather52: move phony targets to main Makefile
- modules/machine/spi: move enable-guard to prevent wrong includes
- nrfx_config: move back nrf52832 to use non-EasyDMA SPI
- move pyb module to boards module
- add support for reading output pin state
- generalize feather52 target
- bluetooth: add support for s132/s140 v6, remove s132 v2/3/5
- boards: check for stack/heap size using an assert
- quick-fix on const objects with open array dimension in objtuples
- bluetooth: replace BLE REPL (WebBluetooth) URL
- add explicit make flag for oofatfs
- compile nlr objects with -fno-lto flag
- upgrade to nrfx 1.1.0
- drivers: add license text to ticker.h and softpwm.h
- use mp_raise_ValueError instead of nlr_raise(...)
- include $(SRC_MOD) in the build
- Makefile: make sure dependencies for pins_gen.c are correct
- properly use (void) instead of () for function definitions
- boards/microbit: use MICROPY_PY_BUILTINS_FLOAT to detect FP support
- update nrfjprog links to allow to download any version
- drivers/flash: fix incorrect page alignment check
- uos: add mbfs __enter__ and __exit__ handlers
- enable all PWM, RTC and Timer instances for nrf52840
- correct index checking of ADC/PWM/RTCounter instances
- use separate config for each PWM instance
- uart: remove unused UART.char_width field
- uart: fix UART.writechar() to write just 1 byte
- bluetooth: set GAP_ADV_MAX_SIZE to 31 (s132/s140)
- bluetooth: update BLE stack download script

pic16bit port:
- update to compile with latest xc16 v1.35 compiler

teensy port:
- add own uart.h to not rely on stm32's version of the file

zephyr port:
- README: hint about existence of qemu_x86_nommu
- main: after builtin testsuite, drop to REPL
- mpconfigport.h: enable uhashlib and ubinascii modules
- modzsensor: zephyr sensor subsystem bindings
- prj_base.conf: enable DHCP and group static IPs together
- add prj_disco_l475_iot1.conf with sensor drivers
- Makefile: add kobj_types_h_target to Z_EXPORTS
- prj_base.conf: remove outdated CONFIG_NET_NBUF_RX_COUNT option
- prj_qemu_x86.conf: remove outdated CONFIG_RAM_SIZE
- rename CONFIG_CONSOLE_PULL to CONFIG_CONSOLE_SUBSYS
- prj_base.conf: update for net_config subsys refactor
- CMakeLists: update for latest Zephyr CMake usage refactorings

docs:
- library: add documentation for ucollections.deque
- ucryptolib: add docs for new ucryptolib module
- usocket: getaddrinfo: describe af/type/proto optional params
- usocket: minor fixes to grammar of getaddrinfo
- uos: make it clear that block device block_num param is an index
- ure: document sub(), groups(), span(), start() and end()
- ure: document some more supported regex operators
- pyboard: for latex build, use smaller quickref jpg, and no gifs
- library: remove "only" directive from all pyb module docs
- library/machine.UART: remove conditional docs for wipy port
- library/machine: remove conditional docs for wake_reason function
- library/machine: remove conditional docs for rng function
- library/index: remove all conditionals from library index
- library/index: add hint about using help('modules') for discovery
- reference/index: remove conditional for inline asm docs
- library/machine: remove conditionals in machine class index
- move WiPy specific Timer class to separate doc file
- library/machine.I2C.rst: clarify availability of primitive I2C ops
- library/machine.UART.rst: specify optional txbuf and rxbuf args
- library/pyb: add deprecation warning for mount and old block proto
- pyboard: fix to use Sphinx style for internal/external links
- library/machine.SPI: add note about baudrate imprecision
- library/network: move specific network classes to their own file
- library/network: make AbstractNIC methods layout correctly
- unify all the ports into one set of documentation
- remove sphinx_selective_exclude, it's no longer used
- wipy: fix links to network.Server, and markup for boot.py
- uselect: describe more aspects of poll.register/modify behavior
- machine.Pin: add note regarding irq handler argument
- machine.Pin: document "hard" argument of Pin.irq method
- uio: document StringIO/BytesIO(alloc_size) constructors
- library/uctypes: add examples and make general updates
- conf.py: use https for intersphinx link to docs.python.org
- ure: fully describe supported syntax subset, add example
- differences: clarify the differences are against Python 3.4
- add initial docs for esp32 port, including quick-ref and general
- library: add documentation for esp32 module

travis:
- install explicit version of urllib3 for coveralls
- use build stages and parallel jobs under Travis CI
- add nrf port to Travis CI build

examples:
- embedding: add code markup and fix typo in README.md
- embedding: fix reference to freed memory, lexer src name
- embedding: fix hard-coded MP_QSTR_ value
- unix/ffi_example: clean up and update the ffi example

README:
- update list of ports to include esp32 and nrf
- remove references to "make axtls", it's no longer needed
- remove text about selecting different ports in the docs

Parser size reduced, new Python stack, stm32 improvements, new esp32 …

…port

This release brings some significant size reductions to the parser, as well
as removal of unused code and additional tests to improve coverage of the
core.  A new optional, internal Python stack is introduced for scoped
allocation and can be used instead of alloca to provide more efficient and
flexible temporary memory; see MICROPY_ENABLE_PYSTACK.  There have been
many improvements and internal code refactors of the stm32 port, and the
port to the Espressif ESP32 SoC has been merged from its development
repository.

Compared to the last release the change in code size is (in bytes, using
gcc 7.3):

   bare-arm: -1832
minimal x86: -2608
   unix x64: -5129
unix nanbox: +1024
      stm32: +2120
     cc3200:  -928
    esp8266:  +336

The decrease is mainly due to the reduced size of the parser, where the
table of rule pointers was compressed to a table of offsets.  The increase
in the stm32 and esp8266 ports is due to additional features, such as more
colour formats in the framebuf module and the addition of ujson.dump().

Code coverage (measured by gcov) has improved since the last version
(v1.9.3 on the left, v1.9.4 on the right):

py:     15202/15447 = 98.4%  ->  15391/15513 = 99.2%
extmod:  2227/ 2363 = 94.2%  ->   2291/ 2430 = 94.3%

Changes and additions seen by the Python user include: improvement of dir()
and tab-completion to list all available attributes of an object; addition
of efficient ucollections.deque type with fixed size; better handling and
polling support of sockets that get into an error state; implementation of
key and cert keyword arguments in ussl.wrap_socket (for axtls);
uos.ilistdir now return 4-tuples with the file size in the fourth position.

Changes at the C level include: removal of "make_qstr_if_not_already"
argument from mp_obj_new_str; rename of mp_exc_recursion_depth to
mp_raise_recursion_depth; removal of mp_const_MemoryError_obj; switching
of stream close operation from method to ioctl; refactoring of how native
emitter code is compiled with a file per architecture.

The stm32 port has seen a lot of improvements and additions, as well as
some significant internal refactoring to better support configuring custom
boards.  STM32F7 support is improved, USB HS is supported for F723 and
F733, the CAN class has improvements to handle bus errors, ctrl-C can
now interrupt running code when the REPL is over UART, and the ADC class
added the read_timed_multi static method.  Board configuration has seen
some internal changes, in particular with setting LD_FILES, TEXT0_ADDR,
and TEXT1_ADDR in mpconfigboard.mk (previously LD_FILE, FLASH_ADDR,
TEXT_ADDR).  The pin_X and pyb_pin_X identifiers have been changed to be
pointers to objects rather than objects, and main is renamed to stm32_main.

A detailed list of changes follows.

py core:
- compile: use alloca instead of qstr_build when compiling import name
- mpconfig: introduce reusable MP_HTOBE32(), etc. macros
- objtype: mp_obj_new_type: name base types related vars more clearly
- objnamedtuple: add _asdict function if OrderedDict is supported
- emitnative: clean up asm macro names so they have dest as first arg
- mkenv.mk: use $(PYTHON) consistently when calling Python tools
- objstr: remove "make_qstr_if_not_already" arg from mp_obj_new_str
- objstr: make mp_obj_new_str_of_type check for existing interned qstr
- objstr: when constructing str from bytes, check for existing qstr
- add config option to disable multiple inheritance
- objnamedtuple: allow to reuse namedtuple basic functionality
- objfloat: allow float() to parse anything with the buffer protocol
- modbuiltins: slightly simplify code in builtin round()
- runtime: simplify handling of containment binary operator
- opmethods: include the correct header for binary op enums
- runtime: add MP_BINARY_OP_CONTAINS as reverse of MP_BINARY_OP_IN
- parsenum: improve parsing of floating point numbers
- objdict: reuse dict-view key iterator for standard dict iterator
- annotate func defs with NORETURN when their corresp decls have it
- qstr: rewrite find_qstr to make manifest that it returns a valid ptr
- gc: in gc_realloc, convert pointer sanity checks to assertions
- objgenerator: remove unreachable code for STOP_ITERATION case
- misc.h: add m_new_obj_var_with_finaliser()
- mp_call_function_*_protected(): pass-thru return value if possible
- modbuiltins: use standard arg-parsing helper func for builtin print
- mpprint: make "%p" format work properly on 64-bit systems
- mpprint: support "%lx" format on 64-bit systems
- malloc: allow to use debug logging if !MICROPY_MALLOC_USES_ALLOCATED_SIZE
- gc: add CLEAR_ON_SWEEP option to debug mis-traced objects
- emitbc, asmbase: only clear emit labels to -1 when in debug mode
- asmbase: revert removal of clearing of label offsets for native emit
- objint_longlong: check for zero division/modulo
- runtime: when tracing unary/binary ops, output op (method) name
- gc: factor out a macro to trace GC mark operations
- gc: in sweep debug output, print pointer as a pointer
- objfun: factor out macro for decoding codestate size
- objfun, vm: add comments on codestate allocation in stackless mode
- objfun: factor out macro for initializing codestate
- mkrules.mk: add "clean-frozen" target to clean frozen script/modules dir
- runtime: move mp_exc_recursion_depth to runtime and rename to raise
- introduce a Python stack for scoped allocation
- convert all uses of alloca() to use new scoped allocation API
- runtime: use the Python stack when building *arg and **kwarg state
- objexcept: use INT_FMT when printing errno value
- extend nan-boxing config to have 47-bit small integers
- objtype: implement better support for overriding native's __init__
- objtype: refactor object's handling of __new__ to not create 2 objs
- builtinimport: call __init__ for modules imported via a weak link
- objgenerator: allow to pend an exception for next execution
- map: don't include ordered-dict mutating code when not needed
- mpz: fix pow3 function so it handles the case when 3rd arg is 1
- modio: use correct config macro to enable resource_stream function
- malloc: remove unneeded code checking m_malloc return value
- nlrthumb: fix use of naked funcs, must only contain basic asm code
- nlr: clean up selection and config of NLR implementation
- nlr: factor out common NLR code to macro and generic funcs in nlr.c
- parse: split out rule name from rule struct into separate array
- parse: break rule data into separate act and arg arrays
- parse: pass rule_id to push_result_rule, instead of passing rule_t*
- parse: pass rule_id to push_result_token, instead of passing rule_t*
- parse: remove rule_t struct because it's no longer needed
- parse: compress rule pointer table to table of offsets
- parse: update debugging code to compile on 64-bit arch
- parse: fix macro evaluation by avoiding empty __VA_ARGS__
- mpz: simplify handling of borrow and quo adjustment in mpn_div
- mpz: in mpz_as_str_inpl, convert always-false checks to assertions
- nlr: fix nlr functions for 64bit ports built with gcc on Windows
- compile: combine compiler-opt of 2 and 3 tuple-to-tuple assignment
- objtype: check and prevent delete/store on a fixed locals map
- modbuiltins: for builtin_chr, use uint8_t instead of char for array
- vm: simplify stack sentinel values for unwind return and jump
- parsenum: fix parsing of floats that are close to subnormal
- objfloat: fix case of raising 0 to -infinity
- unicode: clean up utf8 funcs and provide non-utf8 inline versions
- modbuiltins: simplify casts from char to byte ptr in builtin ord
- objrange: implement (in)equality comparison between range objects
- objexcept: remove long-obsolete mp_const_MemoryError_obj
- nlrthumb: do not mark nlr_push as not returning anything
- pystack: use "pystack exhausted" as error msg for out of pystack mem
- objdict: disallow possible modifications to fixed dicts
- gc: reduce code size by specialising VERIFY_MARK_AND_PUSH macro
- gc: rename gc_drain_stack to gc_mark_subtree and pass it first block
- gc: make GC stack pointer a local variable
- qstr: add QSTR_TOTAL() macro to get number of qstrs
- modbuiltins: simplify and generalise dir() by probing qstrs
- repl: generalise REPL autocomplete to use qstr probing
- objstr: protect against creating bytes(n) with n negative
- objmodule: factor common code for calling __init__ on builtin module
- builtinimport: add compile-time option to disable external imports
- modmicropython: allow to have stack_use() func without mem_info()
- objstr: remove unnecessary check for positive splits variable
- objint: use MP_OBJ_IS_STR_OR_BYTES macro instead of 2 separate ones
- objdeque: implement ucollections.deque type with fixed size
- objdeque: protect against negative maxlen in deque constructor
- objdeque: use m_new0 when allocating items to avoid need to clear
- py.mk: split list of uPy sources into core and extmod files
- py.mk: remove .. path component from list of extmod files
- use "GEN" consistently for describing files generated in the build
- compile: adjust c_assign_atom_expr() to use return instead of goto
- asm*.c: remove unnecessary check for num_locals<0 in asm entry func
- mpz: in mpz_clone, remove unused check for NULL dig
- mpstate.h: add repl_line state for MICROPY_REPL_EVENT_DRIVEN
- vm: fix case of handling raised StopIteration within yield from
- vm: simplify handling of special-case STOP_ITERATION in yield from
- formatfloat: fix rounding of %f format with edge-case FP values
- formatfloat: fix case where floats could render with a ":" character
- formatfloat: fix case where floats could render with negative digits
- objint: remove unreachable code checking for int type in format func
- misc.h: remove unused count_lead_ones() inline function
- obj.h: clean up by removing commented-out inline versions of macros
- obj.h: move declaration of mp_obj_list_init to objlist.h
- makeqstrdefs.py: optimise by using compiled re's so it runs faster
- objexcept: make MP_DEFINE_EXCEPTION public so ports can define excs
- runtime: check that keys in dicts passed as ** args are strings
- runtime: be sure that non-intercepted thrown object is an exception
- vm: don't do unnecessary updates of ip and sp variables
- vm: optimise handling of stackless mode when pystack is enabled
- modsys: don't compile getsizeof function if feature is disabled
- don't include mp_optimise_value or opt_level() if compiler disabled
- objint: simplify LHS arg type checking in int binary op functions
- objstr: in find/rfind, don't crash when end < start
- stream: switch stream close operation from method to ioctl
- objgenerator: check stack before resuming a generator
- refactor how native emitter code is compiled with a file per arch
- nlrthumb: fix Clang support wrt use of "return 0"
- mperrno: define MP_EWOULDBLOCK as EWOULDBLOCK, not EAGAIN
- stream: use uPy errno instead of system's for non-blocking check
- obj.h: fix math.e constant for nan-boxing builds
- modbuiltins, repl: start qstr probing from after empty qstr
- runtime: add mp_load_method_protected helper which catches exceptions
- modbuiltins: make built-in hasattr work properly for user types
- repl: use mp_load_method_protected to prevent leaking of exceptions
- modbuiltins: in built-in dir make use of mp_load_method_protected
- modbuiltins: make built-in dir support the __dir__ special method
- objdeque: fix sign extension bug when computing len of deque object

extmod:
- modussl_axtls: socket_read: Handle EAGAIN
- moduhashlib: enable SHA1 hashing when using "mbedtls" library
- vfs_fat: mount FatFS on creation so VFS methods can be used
- modussl_axtls: implement key and cert kw args to wrap_socket
- modlwip: commit TCP out data to lower layers if buffer gets full
- machine_signal: change VLA to use new scoped allocation API
- modure: convert alloca() to use new scoped allocation API
- modussl_mbedtls: clean up mbedtls state when error during setup
- modframebuf: add 2-bit color format (GS2_HMSB)
- modframebuf: add 8-bit greyscale format (GS8)
- vfs_fat_file: implement SEEK_CUR for non-zero offset
- modujson: implement ujson.dump() function
- vfs_fat: move ilistdir implementation from misc to main file
- vfs_fat: merge remaining vfs_fat_misc.c code into vfs_fat.c
- vfs_fat: make fat_vfs_open_obj wrapper public, not its function
- vfs_fat: remove declaration of mp_builtin_open_obj
- vfs_fat_diskio: use a C-stack-allocated bytearray for block buf
- machine_spi: make SPI protocol structure public
- vfs_fat: add file size as 4th element of uos.ilistdir tuple
- re1.5: fix compilecode.c compile problem on IAR tool chain
- modlwip: check if getaddrinfo() constraints are supported or not
- vfs: delegate import_stat to vfs.stat to allow generic FS import
- uzlib: fix C-language sequencing error with uzlib_get_byte calls
- modlwip: in ioctl handle case when socket is in an error state

lib:
- tinytest: move from tools/tinytest
- upytesthelper: add MicroPython test helper layer on top of tinytest
- tinytest: clean up test reporting in the presence of stdout output
- utils/pyexec.h: include py/obj.h because its decls are needed
- utils/pyexec: update to work with new MICROPY_HW_ENABLE_USB option
- stm32lib: update library to include support for STM32H7 MCUs
- stm32lib: update library for fix to H7 SPI strict aliasing error
- axtls: update, exposes AES functions to implement ECB cipher mode

drivers:
- nrf24l01: make driver and test run on pyboard, ESP8266, ESP32
- display/ssd1306: make SSD1306 class inherit from FrameBuffer
- sdcard: support old SD cards (<=2GB)
- sdcard: avoid allocation on the heap
- sdcard: update doc for ESP8266 to use correct SPI number
- cc3200: update to work with new stm32 SPI API
- sdcard: update SD mounting example code for ESP8266
- bus: add QSPI abstract type with software QSPI implementation
- memory/spiflash: add support for QSPI interface
- bus: pull out software SPI implementation to dedicated driver
- memory/spiflash: change to use low-level SPI object not uPy one

tools:
- mpy-tool.py: implement freezing of Ellipsis const object
- gen-cpydiff.py: update executable paths to point to new ports dir
- tinytest-codegen.py: generate code for upytesthelper
- tinytest-codegen: wrap lines of exclude_tests
- tinytest-codegen: more excludes after enabling expected output match
- tinytest-codegen: take --target= option for test set selection
- pydfu.py: call set_configuration() on fresh USB device object
- tinytest-codegen: add --stdin switch instead of recently added --target
- tinytest-codegen: ignore system locale, write output in UTF-8
- upip: upgrade upip to 1.2.4

tests:
- net_hosted: add test for socket connect() and poll() behaviour
- basics: add test for containment of a subclass of a native type
- basics/builtin_range: add test for corner case of range slicing
- basics/builtin_locals: add test for using locals() in class body
- cpydiff: add difference-test for second arg of builtin next()
- cpydiff: fix markup where "`" (xref) was used instead of "``" (code)
- heapalloc_*: refactor some tests to work in strict stackless mode
- heapalloc, heapalloc_super: skip in strict stackless mode
- basics: add test for overriding a native base-class's init method
- extmod: add test which subclasses framebuf.FrameBuffer
- cpydiff: update subclassing Exception case and give work-around
- fix few test for proper "skipped" detection with qemu-arm's tinytest
- run-tests: add --list-tests switch
- add tests to improve coverage of py/objtype.c
- run-tests: fix handling of --list-tests wrt skipped tests
- run-tests: add composable --include and --exclude options
- run-tests: don't test for --target=unix with "pyb is None"
- run-tests: skip running feature checks for --list-tests/--write-exp
- basics: add more set tests to improve coverage of py/objset.c
- extmod/uhashlib_sha256: add test for hashing 56 bytes of data
- float/builtin_float_hash: add test to improve objfloat.c coverage
- unix: add test for printf with %lx format
- basics/generator_pend_throw: add test for just-started generator
- basics/builtin_pow3: add tests for edge cases of pow3
- add some more tests to improve coverage of py/parse.c
- extmod: add some uctypes tests to improve coverage of that module
- basics/memoryerror: add test for out-of-memory using realloc
- basics: rename remaining tests that are for built-in functions
- unix: add coverage test for calling mp_obj_new_bytearray
- automatically skip tests that require eval, exec or frozenset
- rewrite some tests so they can run without needing eval/exec
- run-tests: capture any output from a crashed uPy execution
- basics/deque*: tests for ucollections.deque
- basics: add tests to improve coverage of py/objdeque.c
- basics: add test for calling a subclass of a native class
- stress: add test to create a dict beyond "maximum" rehash size
- unix: add coverage tests for mpz_set_from_float, mpz_mul_inpl
- extmod/vfs_fat_fileio1: add test for failing alloc with finaliser
- extmod/uzlib_decompress: add uzlib tests to improve coverage
- float: adjust float-parsing tests to pass with only a small error
- unix: add coverage test for VM executing invalid bytecode
- basics/gc1: add test which triggers GC threshold
- extmod/vfs_fat_fileio1: add test for calling file obj finaliser
- unix: add coverage tests for various GC calls
- move heap-realloc-while-locked test from C to Python
- unix: add coverage test for uio.resource_stream from frozen str
- extmod/time_ms_us: add test for calling ticks_cpu()
- extmod/time_ms_us: fix ticks tests, ticks_diff args are reversed
- basics/builtin_enumerate: add test for many pos args to enumerate
- cpydiff: indent workaround code snippet so it formats correctly
- pyb: update CAN test to expect that auto_restart is printed
- pyb/can: update to test pyb.CAN restart, state, info, inplace recv
- basics/iter1.py: add more tests for walking a user-defined iter
- basics: add test for use of return within try-except
- basics/int_big1.py: add test converting str with non-print chars
- basics: modify int-big tests to prevent constant folding
- stress: add test to verify the GC can trace nested objects
- basics/int_big1.py: add test for big int in mp_obj_get_int_maybe
- basics: add test for subclassing an iterable native type
- basics: add tests for edge cases of nan-box's 47-bit small int
- basics/class_super.py: add tests for store/delete of super attr
- basics/string_compare.py: add test with string that hashes to 0
- micropython: add set of tests for extreme cases of raising exc's
- stress/recursive_gen: add test for recursive gen with iter
- move recursive tests to the tests/stress/ subdir
- pyb/adc.py: fix test so that it really does test ADC values
- pyb: add test for pyb.ADCAll class
- io/bytesio_ext2: remove dependency on specific EINVAL value
- run-tests: support esp32 as a target for running the test suite
- cpydiff: remove core_function_unpacking now that it succeeds
- cpydiff: remove types_str_decodeerror now that it succeeds
- cpydiff: remove working cases from types_float_rounding
- cpydiff: remove types_int_tobytesfloat now that it doesn't fail
- float/float_parse: allow test to run on 32-bit archs

minimal port:
- README: update text to better describe what "make run" does
- Makefile: explicitly include lib/utils/printf.c in build
- Makefile: only build with core source files

unix port:
- moduselect: add .dump() method for debugging
- mpconfigport: disable uio.resource_stream()
- add support for using the Python stack
- Makefile: coverage: allow user to pass CFLAGS_EXTRA
- mpconfigport.h: allow to override stackless options from commandline
- mpconfigport_coverage.h: enable MICROPY_PY_IO_RESOURCE_STREAM
- mpconfigport_coverage: enable range (in)equality comparison
- coverage: allow coverage tests to pass with debugging disabled

windows port:
- mpconfigport: provide off_t definition for MSVC port
- mpconfigport: enable some features, including the Python stack
- add Appveyor CI builds for windows mingw port

qemu-arm port:
- rework "test" target using upytesthelper
- test_main: clean up invocation of tinytest_main()
- test_main: include setjmp.h because it's used by gc_collect

stm32 port:
- boards/NUCLEO_F429ZI: incr CPU freq to 168MHz to get USB working
- boards: add support for NUCLEO-F746ZG evaluation board
- boards/stm32f767_af.csv: update AF table based on datasheet
- boards/*_af.csv: make consistent use of JTMS, JTCK, SWDIO, SWCLK
- add support for using the Python stack
- usbdev: pass thru correct val for SCSI PreventAllowMediumRemoval
- use corrected capitalization of HAL_SD_CardStateTypedef
- allow to build a board without any hardware I2C ports defined
- uart: add support for 7-bit modes: 7N1 and 7N2
- uart: support board configs with CTS/RTS on UART6
- i2c: fix bug with I2C4 initialisation
- i2c: support more I2C baudrates for F746, and more F7 MCUs
- spi: if MICROPY_HW_SPIn_MISO undefined, do not claim pin on init
- modmachine: handle case of no MICROPY_PY_MACHINE_I2C
- add support for DHT11/DHT22 sensors
- spi: make SPI DMA wait routine more power efficient by using WFI
- sdcard: make SD wait routine more power efficient by using WFI
- usbdev: reduce dependency on py header files
- usbdev: combine all str descriptor accessor funcs into one func
- can: support MCUs without a CAN2 peripheral
- improve support for STM32F722, F723, F732, F733 MCUs
- modmachine: in freq(), select flash latency value based on freq
- sdcard: only define IRQ handler if using SDMMC1 peripheral
- sdcard: use maximum speed SDMMC clock on F7 MCUs
- usbdev: add support for MSC-only USB device class
- usb: allow board to select which USBD is used as the main one
- usbdev: add support for high-speed USB device mode
- i2c: use macros instead of magic numbers for I2C speed grades
- spi: add support for a board naming SPI peripherals 4, 5 and 6
- rng: simplify RNG implementation by accessing raw peripheral regs
- spi: allow SPI peripheral state to persist across a soft reset
- i2c: allow I2C peripheral state to persist across a soft reset
- spi: provide better separation between SPI driver and uPy objs
- update LCD and network drivers to work with new SPI API
- spi: accept machine.SPI object in spi_from_mp_obj() function
- rtc: fix rtc_info flags when LSE fails and falls back to LSI
- rtc: fix RTC init to use LSI if LSI is already selected on boot
- rtc: add compile-time option to set RTC source as LSE bypass
- main: reorder some init calls to put them before soft-reset loop
- main: remove need for first_soft_reset variable
- add mpconfigboard_common.h with common/default board settings
- boards: remove all config options that are set to defaults
- usbdev: fix USBD setup request handler to use correct recipient
- update HAL macro and constant names to use newer versions
- timer: support MCUs that don't have TIM4 and/or TIM5
- introduce MICROPY_HW_ENABLE_USB and clean up USB config
- boards: update all boards to work with new USB configuration
- factor out flash and SPI block-device code to separate files
- change header include guards from STMHAL to STM32 to match dir
- add board config option to enable/disable the ADC
- use "GEN" for describing files generated in the build
- flash: use FLASH_TYPEPROGRAM_WORD to support newer HALs
- move MCU-specific cfg from mphalport.h to mpconfigboard_common.h
- spibdev: update to work with new spiflash driver
- spibdev: add option to configure SPI block dev to use QSPI flash
- storage: add option for bdev to supply readblock/writeblocks
- spibdev: convert to use multiple block read/write interface
- qspi: add hardware QSPI driver, with memory-map capability
- i2c: on F4 MCUs report the actual I2C SCL frequency
- boards/stm32f767_af.csv: add ADC column to pin capability list
- boards/NUCLEO_F767ZI: update pins list to include 3 extra pins
- boards: add stm32h743_af.csv file describing H7 GPIO alt funcs
- boards: add stm32h743.ld linker script
- boards: add new NUCLEO_H743ZI board configuration files
- Makefile: add settings to support H7 MCUs
- flash: add flash support for H7 MCUs
- system_stm32: add H7 MCU system initialisation
- mphalport: use GPIO BSRRL/BSRRH registers for H7 MCUs
- wdt: add WDT support for H7 MCUs
- uart: add UART support for H7 MCUs
- timer: add Timer support for H7 MCUs
- modmachine: support basic H7 MCU features
- usbd_conf: add USB support for H7 MCUs
- stm32_it: add support for H7 MCUs
- dma: add DMA support for H7 MCUs
- rtc: add RTC support for H7 MCUs
- extint: add EXTI support for H7 MCUs
- mpconfigboard_common: add STM32H7 common configuration
- main: enable D2 SRAM1/2/3 clocks on H7 MCUs
- boards: add startup_stm32h7.s for H7 series specific startup
- boards: add startup_stm32f7.s for F7 series specific startup
- boards: add startup_stm32f4.s for F4 series specific startup
- boards: add startup_stm32l4.s for L4 series specific startup
- Makefile: use separate startup file for each MCU series
- remove startup_stm32.S, now provided in boards/ for each MCU
- usbd_conf.h: add include of stdint.h to fix compilation issues
- system_stm32: fix CONFIG_RCC_CR_2ND value to use bitwise or
- storage: merge all misc block-dev funcs into a single ioctl func
- storage: make spi_bdev interface take a data pointer as first arg
- storage: remove all SPI-flash bdev cfg, to be provided per board
- storage: introduce MICROPY_HW_ENABLE_INTERNAL_FLASH_STORAGE cfg
- boards/STM32L476DISC: provide SPI-flash bdev config
- storage: provide support for a second block device
- qspi: do an explicit read instead of using memory-mapped mode
- boards/STM32L476DISC: enable CAN peripheral
- can: improve can.recv() so it checks for events, eg ctrl-C
- can: use enums to index keyword arguments, for clarity
- can: add "auto_restart" option to constructor and init() method
- can: add CAN.restart() method so controller can leave bus-off
- can: add CAN.state() method to get the state of the controller
- can: add CAN.info() method to retrieve error and tx/rx buf info
- use STM32xx macros instead of MCU_SERIES_xx to select MCU type
- can: add "list" param to CAN.recv() to receive data inplace
- dma: enable H7 DMA descriptors
- i2c: add H7 I2C timing configurations
- boards/NUCLEO_H743ZI: enable hardware I2C support
- boards/NUCLEO_H743ZI: disable uSD transceiver
- Makefile: re-enable strict aliasing optimisation for ST HAL files
- consolidate include of genhdr/pins.h to single location in pin.h
- qspi: don't take the address of pin configuration identifiers
- *bdev.c: eliminate dependency on sys_tick_has_passed
- boards: allow boards to have finer control over the linker script
- Makefile: rename FLASH_ADDR/TEXT_ADDR to TEXT0_ADDR/TEXT1_ADDR
- Makefile: allow a board to config either 1 or 2 firmware sections
- boards: add common_basic.ld for a board to have a single section
- boards: add common_bl.ld for boards that need a bootloader
- system_stm32: set VTOR pointer from TEXT0_ADDR
- boards/stm32f767.ld: add definition of FLASH_APP
- boards/stm32h743.ld: remove include of common.ld
- boards/NUCLEO_H743ZI: update to build with new linker management
- dma: remove H7 SDMMC DMA descriptors
- sdcard: add H7 SD card support
- boards/NUCLEO_H743ZI: enable SD card support
- change pin_X and pyb_pin_X identifiers to be pointers to objects
- boards/STM32L476DISC: update to not take the address of pin objs
- add custom, optimised Reset_Handler code
- main: rename main to stm32_main and pass through first argument
- main: only update reset_mode if board doesn't use a bootloader
- mphalport: use MCU regs to detect if cycle counter is started
- dac: add support for H7 MCUs
- boards/NUCLEO_H743ZI: enable DAC peripheral
- i2c: update HAL macros to use new __HAL_RCC prefix
- i2c: fully support peripheral I2C4
- main: guard usb_mode lines in default boot.py by relevant #if
- adc: fix verification of ADC channel 16 for F411 MCUs
- adc: add read_timed_multi() static method, with docs and tests
- adc: optimise read_timed_multi() by caching buffer pointers
- dac: add buffering argument to constructor and init() method
- adc: factor code to optimise adc_read_channel and adc_read
- adc: fix config of EOC selection and Ext-Trig for ADC periph
- adc: factor common ADC init code into adcx_init_periph()
- pin: in pin AF object, remove union of periph ptr types
- can: allow CAN pins to be configured per board
- stm32_it: add IRQ handler for I2C4
- allow a board to configure the HSE in bypass mode
- main: allow a board to configure the label of the flash FS
- sdcard: implement BP_IOCTL_SEC_COUNT to get size of SD card
- rng: set RNG clock source for STM32H7
- boards/NUCLEO_H743ZI: enable RNG for this board
- uart: allow ctrl-C to issue keyboard intr when REPL is over UART
- uart: allow ctrl-C to work with UARTs put on REPL via os.dupterm
- introduce MICROPY_PY_STM config to include or not the stm module
- dac: support MCUs that don't have TIM4/5 and use new HAL macro
- rename i2c.c to pyb_i2c.c
- rename legacy pyb.I2C helper functions to start with pyb_i2c_
- i2c: add low-level I2C driver for F7 MCUs
- machine_i2c: provide hardware I2C for machine.I2C on F7 MCUs
- system_stm32: reconfigure SysTick IRQ priority for L4 MCUs
- boards/NUCLEO_H743ZI: use priority 0 for SysTick IRQ
- adc: add support for H7 MCU series
- boards/NUCLEO_H743ZI: enable ADC peripheral
- mphalport: add mp_hal_pin_config_speed() to select GPIO speed
- usbd_conf: use mp_hal_pin_config() instead of HAL_GPIO_Init
- dac: use mp_hal_pin_config() instead of HAL_GPIO_Init()
- boards: update pins.csv to include USB pins where needed
- mphalport: support ADC mode on a pin for L4 MCUs
- adc: use mp_hal_pin_config() instead of HAL_GPIO_Init()
- dac: make deinit disable the output buffer on H7 and L4 MCUs
- dac: implement printing of a DAC object
- mphalport: optimise the way that GPIO clocks are enabled
- flash: remove unused src parameter from flash_erase()
- dma: always deinit/reinit DMA channels on L4 MCUs
- irq: define IRQ priorities directly as encoded hardware values
- main: clean up and optimise initial start-up code of the MCU
- dma: fix duplicate typedef of struct, it's typedef'd in dma.h
- don't use %lu or %lx for formatting, use just %u or %x
- Makefile: use -O2 to optimise compilation of lib/libc/string0.c
- i2c: make sure stop condition is sent after receiving addr nack
- usb: fix broken pyb.have_cdc() so it works again
- usb: use correct type for USB HID object
- README: update to reflect current MCU support

teensy port:
- update GPIO speed consts to align with changes in stm32 port

esp8266 port:
- etshal.h: make function prototypes compatible with ESP SDK 2.1.0+
- README: emphasize the need to change default WiFi password
- README: add section on using upip
- esp8266_common.ld: put .text of more libs into .irom0.text
- modules/webrepl_setup: fix first-time enable of WebREPL
- modnetwork: make sure to intern string passed to .config("param")
- machine_hspi: after an SPI write wait for last byte to transfer
- modules: move dht.py driver to drivers/dht directory
- esppwm: clip negative duty numbers to 0
- README.md: update build instruction to reflect new ports dir
- uart: allow to compile with event-driven REPL
- modnetwork: implement WLAN.status('rssi') for STA interface
- esppwm: always start timer to avoid glitch from full to nonfull
- esp_mphal.h: fix I2C glitching by using input mode for od_high
- modnetwork: allow to get ESSID of AP that STA is connected to
- disable DEBUG_PRINTERS for 512k build

esp32:
- add new port to Espressif ESP32 SoC
- modnetwork: give better error msgs for AP timeout and not-found
- modsocket: implement setsockopt(IP_ADD_MEMBERSHIP)
- mpconfigport.h: add missing uhashlib
- mphalport.h: make mp_hal_pin_<dir> select gpio on the pad
- call initialization function on sha1 and sha256
- implement machine.WDT() class
- README: update general description of port to add avail features
- modutime.c: add localtime and mktime functions
- machine_pwm: always set the channel in the PWM object
- update to latest ESP IDF
- modules: symlink in ntptime.py from esp8266/modules
- modnetwork.c: fix for setting DNS with network.WLAN.ifconfig()
- mpconfigport.h: enable ussl finaliser
- implement wired Ethernet via network.LAN()
- mpconfigport.h: enable websocket module
- modesp: add osdebug() function to disable or change IDF logging
- Makefile: support using IDF_PATH as the env var to the IDF source
- add custom partitions.csv file with uPy specific size
- machine_hw_spi: fix large HW SPI transfers by splitting them up
- README: update toolchain setup
- machine_uart: fix check of UART id so it only allows valid UARTs
- machine_rtc: add RTC class to machine module with sleep impl
- modesp32: add new module "esp32" to support extra wake features
- machine_rtc: move export declaration from .c to common .h file
- modnetwork: implement dhcp_hostname for WLAN.config()
- update to the latest ESP IDF
- main: allocate the uPy heap via malloc instead of on the bss
- modsocket: allow getaddrinfo() to take up to 6 args
- modnetwork: implement status('stations') to list STAs in AP mode
- machine_uart: return None from UART read if no data is available
- machine_uart: remove UART event queue object
- README.md: fix typo readme
- mphalport: use esp_timer_get_time instead of gettimeofday
- mphalport: improve mp_hal_delay_us so it handles pending events
- mphalport: improve mp_hal_stdout_tx_XXX functions
- add support for and enable uos.dupterm()
- modsocket: add support for registering socket event callbacks
- mpconfigport: enable webrepl module and socket events
- modules: add support scripts for WebREPL
- add support for the esp32's ULP
- modnetwork: allow to get ESSID of AP that STA is connected to
- README: add --init to submodule update command
- modsocket: correctly handle reading from a peer-closed socket
- use mp_rom_map_elem_t and MP_ROM_xxx macros for const dicts
- modsocket: check for pending events during blocking socket calls

zephyr port:
- README: "make qemu" was replaced with "make run"
- Makefile: clean: Remove generated prj_*_merged.conf
- prj_base.conf: force zephyr.bin build output
- Makefile: convert to new CMake-based Zephyr build system
- Makefile: make prj_$(BOARD).conf optional, again
- Makefile: syscall_macros.h generation was moved from CMake to make
- CMakeLists.txt: update for latest Zephyr buildsys changes
- CMakeLists.txt: properly separate CFLAGS parts gotten from CMake
- main: move var declarations to the top of file
- add support for binary with builtin testsuite
- prj_base.conf: bump MAIN_STACK_SIZE to let builtin testsuite run
- Makefile: clean: Clean libmicropython.a too
- main: remove unused do_str() function

docs:
- esp8266/general: TLS limitations: mention also "ussl" module limitations
- ure: add flags arg to ure.compile(), mention that ure.DEBUG is optional
- ure: emphasize not supported features more
- _thread: add a placeholder docs for _thread module
- library/network: enhance AbstractNIC.status to take an argument
- add notes on heap allocation caused by bound method refs
- uselect: poll: Explicitly specify that no-timeout value is -1
- uctypes: tweak descriptor reference to hopefully be easier to follow
- uselect: describe POLLHUP/POLLERR semantics in more details
- library/utime: fix incorrect example with ticks_diff args order
- uselect: ipoll: Fix grammar/wording of one-shot flag description
- glossary: describe the callee-owned tuple concept
- uerrno: fix xref-vs-code markup
- glossary: describe "stream" term
- glossary: describe string interning
- library: add xrefs to "stream" dictionary entry for many modules
- glossary: clarify wording for "baremetal"
- reference/packages: add chapter on distribution packages and deployment
- packages: add quick "Creating distribution packages" section
- packages: mpy_bin2res no longer required to create resources
- conf: reference CPython 3.5 docs
- packages: use "install_dir/" in examples
- packages: explicitly recommend usage of setuptools instead of distutils
- library/index: elaborate uPy libraries intro
- library/pyb.rst: add note about availability of USB MSC-only mode
- esp8266: update PWM doc regarding clipping of min/max values
- esp8266: add a note concerning GPIO16 pull capabilities
- library/ujson: document dump() and load() functions
- library/usocket: make xref to uerrno explicitly a module reference
- library/micropython: describe optimisation levels for opt_level()
- library/uos: create sections for distinct parts and document uname
- library/uos: document mount, umount, VfsFat and block devices
- reference/repl.rst: fix some minor errors in the REPL tutorial
- library/pyb.ADC: document new features for ADCAll
- library/pyb.ADC: remove outdated ADCAll code example
- library: add ussl module to library index for unix port

travis:
- pass -j4 to make to speed up compilation
- update for qemu-arm's testing moved to Makefile.test
- build and test strict stackless build
- add Unix coverage test for script via stdin

Introduction of ports subdirectory where all ports are moved to

The main change in this release is the introduction of a "ports/"
subdirectory at the top-level of the repository, and all of the ports are
moved here.  In the process the "stmhal" port is renamed to "stm32" to
better reflect the MCU that it targets.  In addition, the STM32 CMSIS and
HAL sources are moved to a new submodule called "stm32lib".

The bytecode has changed in this release, compared to the previous release,
and as a consequence the .mpy version number has increased to version 3.
This means that scripts compiled with the previous mpy-cross must be
recompiled to work with this new version.

There have also been various enhancements and optimisations, such as:
check for valid UTF-8 when creating str objects, support for reverse
special binary operations like __radd__, full domain checking in the math
module, support for floor-division and modulo in the viper emitter,
and addition of stack overflow checking when executing a regex.

The stm32 port sees improved support for F7 MCUs, addition of a new board
B_L475E_IOT01A based on the STM32L475, and support for the Wiznet W5500
chipset along with improved socket behaviour.

A detailed list of changes follows.

py core:
- objstr: startswith, endswith: check arg to be a string
- nlrx86,x64: replace #define of defined() with portable macro usage
- objtype: handle NotImplemented return from binary special methods
- objtype: mp_obj_class_lookup: improve debug logging
- map: remove unused new/free functions
- make m_malloc_fail() have void return type, since it doesn't return
- modstruct: in struct.pack, stop converting if there are no args left
- modstruct: check and prevent buffer-read overflow in struct unpacking
- modstruct: check and prevent buffer-write overflow in struct packing
- nlrthumb: get working again on standard Thumb arch (ie not Thumb2)
- objfloat: fix binary ops with incompatible objects
- obj: fix comparison of float/complex NaN with itself
- objtype: implement fallback for instance inplace special methods
- objtuple: properly implement comparison with incompatible types
- objstr: add check for valid UTF-8 when making a str from bytes
- objlist: properly implement comparison with incompatible types
- runtime0.h: move relational ops to the beginning of mp_binary_op_t
- runtime0.h: move MP_BINARY_OP_DIVMOD to the end of mp_binary_op_t
- objtype: make sure mp_binary_op_method_name has full size again
- runtime0.h: put inplace arith ops in front of normal operations
- builtinhelp: simplify code slightly by extracting object type
- runtime: implement dispatch for "reverse op" special methods
- nlrx86: fix building for Android/x86
- builtinhelp: change signature of help text var from pointer to array
- runtime.h: change empty mp_warning macro so var-args are non empty
- modbuiltins: implement abs() by dispatching to MP_UNARY_OP_ABS
- {objfloat,objcomplex}: optimise MP_UNARY_OP_ABS by reusing variables
- mpconfig.h: add note that using computed gotos in VM is not C99
- objstr: strip: don't strip "\0" by default
- objexcept: prevent infinite recursion when allocating exceptions
- stream: remove unnecessary checks for NULL return from vstr_add_len
- vstr: raise a RuntimeError if fixed vstr buffer overflows
- vm: use lowercase letter at start of exception message
- persistentcode: define mp_raw_code_save_file() for any unix target
- add config option to print warnings/errors to stderr
- objfloat: support raising a negative number to a fractional power
- objset: simplify set and frozenset by separating their locals dicts
- objset: check that RHS of a binary op is a set/frozenset
- objset: include the failed key in a KeyError raised from set.remove
- objtype: change type of enum-to-qstr table to uint16_t to save space
- objstr: make empty bytes object have a null-terminating byte
- mpprint: only check for null string printing when NDEBUG not defined
- objtype: clean up unary- and binary-op enum-to-qstr mapping tables
- persistentcode: bump .mpy version number to version 3
- bc: update opcode_format_table to match the bytecode
- modmath: add full checks for math domain errors
- modmath: convert log2 macro into a function
- formatfloat: don't print the negative sign of a NaN value
- formatfloat: use standard isinf, isnan funcs instead of custom ones
- modbuiltins: use existing utf8_get_char helper in builtin ord func
- emitnative: implement floor-division and modulo for viper emitter
- objtype: use CPython compatible method name for sizeof
- objtype: fit qstrs for special methods in byte type
- objtype: define all special methods if requested
- objtype: introduce MICROPY_PY_ALL_INPLACE_SPECIAL_METHODS

extmod:
- modubinascii: only include uzlib/tinf.h when it's really needed
- modussl_mbedtls: allow to compile with MBEDTLS_DEBUG_C disabled
- machine_pinbase: put PinBase singleton in ROM
- re1.5: upgrade to v0.8.2, adds hook for stack overflow checking
- modure: add stack overflow checking when executing a regex
- uos_dupterm: update uos.dupterm() and helper funcs to have index
- uos_dupterm: swallow any errors from dupterm closing the stream
- vfs: replace VLA in proxy func with small, static sized array
- modussl: add finaliser support for ussl objects
- modussl_mbedtls: allow to compile with unix coverage build

lib:
- add new submodule, stm32lib containing STM32 CMSIS and HAL source
- embed/abort_: use mp_raise_msg helper function
- libm: fix tanhf so that it correctly handles +/- infinity args
- libm: remove implementation of log2f, use MP_NEED_LOG2 instead
- axtls: update, support for SSL_EAGAIN return code
- berkeley-db-1.xx: update, allow to override MINCACHE, DEFPSIZE

drivers:
- memory/spiflash: change from hard-coded soft SPI to generic SPI
- display/ssd1306.py: improve performance of graphics methods
- nrf24l01: make nRF24L01 test script more portable
- display/ssd1306: implement SSD1306_I2C poweron method
- display/ssd1306: make poweron() work the same with SSD1306_SPI
- wiznet5k: improve the performance of socket ops with threading
- wiznet5k: get low-level W5500 driver working

tools:
- upip: upgrade to 1.2.2
- pyboard: use repr() when quoting data in error messages
- pyboard: update docstring for additional device support

tests:
- object_new: better messages, check user __new__() method
- class_new: add checks for __init__ being called and other improvements
- class_new: add another testcase for __new__/__init__ interaction
- class_inplace_op: test for inplace op fallback to normal one
- run-bench-tests: update locations of executables, now in ports/
- class_reverse_op: test for reverse arith ops special methods
- run-tests: skip class_inplace_op for minimal profile
- run-tests: fix copy-paste mistake in var name
- cpydiff: add cases for locals() discrepancies
- extmod: add test for ure regexes leading to infinite recursion
- extmod: add test for '-' in character class in regex
- run-tests: close device under test using "finally"
- net_inet: update tls test to work with CPython and incl new site

unix port:
- rename modsocket.c to modusocket.c
- modusocket: remove #if MICROPY_SOCKET_EXTRA code blocks
- enable MICROPY_PY_REVERSE_SPECIAL_METHODS

stm32 port:
- modmachine: make machine.bootloader() work when MPU is enabled
- modmachine: improve support for sleep/deepsleep on F7 MCUs
- compute PLL freq table during build instead of at run time
- modmachine: for F7 MCU, save power by reducing internal volt reg
- boards/pllvalues.py: make script work with both Python 2 and 3
- Makefile: use lib/stm32lib instead of local cmsis and hal files
- remove cmsis and hal files, they are now a submodule
- Makefile: automatically fetch stm32lib submodule if needed
- update to new STM Cube HAL library
- fix clock initialisation of L4 MCUs
- rename stmhal port directory to stm32
- remove unused usbd_msc.c file
- boards: change remaining stm32f4xx_hal_conf.h to unix line ending
- boards: change linker scripts to use "K" instead of hex byte size
- boards: fix I2C1 pin mapping on NUCLEO_F401RE/F411RE boards
- i2c: when scanning for I2C devices only do 1 probe per address
- modnwwiznet5k: release the GIL on blocking network operations
- boards: add new board B_L475E_IOT01A based on STM32L475
- make-stmconst.py: make sure mpz const data lives in ROM
- timer: make pyb.Timer() instances persistent
- mpconfigport.h: add configuration for max periphs on L4 series
- usbdev: make the USBD callback struct const so it can go in ROM
- usbdev: change static function variable to non-static
- usbdev: put all CDC state in a struct
- usbdev: put all HID state in a struct
- usbdev: simplify CDC tx/rx buffer passing
- usbdev: simplify HID tx/rx buffer passing
- usbdev/core: add state parameter to all callback functions
- usbdev: put all state for the USB device driver in a struct
- usbdev: simplify pointers to MSC state and block dev operations
- usbdev: merge all global USB device state into a single struct
- usbdev: make device descriptor callbacks take a state pointer
- usbdev: move all the USB device descriptor state into its struct
- timer: enable ARPE so that timer freq can be changed smoothly
- modnwwiznet5k: get the IP address of an established socket
- boards: fix typos in stm32f767_af.csv table
- usbd_cdc_interface: don't reset CDC output buf on initialisation
- modnwwiznet5k: implement WIZNET5K.isconnected() method
- modusocket: make getaddrinfo() work when passed an IP address
- modusocket: return OSError(-2) if getaddrinfo fails
- mpconfigport.h: add MICROPY_THREAD_YIELD() macro
- modnwwiznet5k: add support for W5500 Ethernet chip
- modnwwiznet5k: increase SPI bus speed to 42MHz
- modnwwiznet5k: implement stream ioctl for the Wiznet driver
- mphalport: improve efficiency of mp_hal_stdout_tx_strn_cooked
- make uos.dupterm() conform to specs by using extmod version

cc3200 port:
- enable micropython.kbd_intr() method
- use standard implementation of keyboard interrupt

esp8266 port:
- rename axtls_helpers.c to posix_helpers.c
- posix_helpers: set ENOMEM on memory alloc failure
- set DEFPSIZE=1024, MINCACHE=3 for "btree" module
- esp_mphal: send data in chunks to mp_uos_dupterm_tx_strn
- modnetwork: add "bssid" keyword arg to WLAN.connect() method
- modules/webrepl_setup: add info about allowed password length

zephyr port:
- Makefile: revamp "test" target after ports were moved to ports/
- use CONFIG_NET_APP_SETTINGS to setup initial network addresses
- switch to interrupt-driven pull-style console

pic16bit port:
- add definition of SEEK_SET to unistd.h

docs:
- pyboard/tutorial: add "timeout=0" to UART in pass-through example
- more xrefs to "MicroPython port" in glossary
- library/network: fix ref to "socket" module (should be "usocket")
- machine.Signal: improve style/grammar and add usage example
- library: add description of "index" parameter to uos.dupterm()
- library/micropython: fix typo in RST formatting
- library/framebuf.rst: generalise constructor to all colour formats
- btree: describe page caching policy of the underlying implementation
- esp8266/tutorial: update neopixel with example of using 4 bbp
- library/network: clarify usage of "bssid" arg in connect() method
- pyboard/quickref: add info for Switch, RTC, CAN, Accel classes
- pyboard/tutorial: update now that yellow LED also supports PWM
- esp8266/quickref: add quickref info for RTC class
- library: add missing cross-ref links for classes in pyb module
- library/network: update docs to state that W5500 is supported
- uselect: document one-shot polling mode
- usocket: elaborate descriptions
- usocket: document inet_ntop(), inet_pton()
- library/network: add dhcp_hostname parameter
- reference/isr_rules: minor typo correction
- ussl: fix module name refs and use "MicroPython port" term
- esp8266/general: add section on TLS limitations
- usocket: document that settimeout() isn't supported by all ports
- ure: add "|" (alternative) to the list of supported operators
- reference/isr_rules.rst: add tutorial on use of micropython.schedule()

travis:
- use --upgrade when pip is installing cpp-coveralls
- update build command now that stm32 Wiznet config has changed

examples:
- hwconfig_console: add .on()/.off() methods

all:
- convert mp_uint_t to mp_unary_op_t/mp_binary_op_t where appropriate
- convert remaining "mp_uint_t n_args" to "size_t n_args"
- make new ports/ sub-directory and move all ports there
- update Makefiles and others to build with new ports/ dir layout
- remove inclusion of internal py header files
- use NULL instead of "" when calling mp_raise exception helpers

README:
- update "Dependencies" section
- add explicit section on contributing
- add gcc and arm-none-eabi-newlib to list of required components

.gitattributes:
- remove obsolete entries for stmhal/hal, stmhal/cmsis
- add entries for files that will move to ports/ dir

Double precision math library and support on pyboard, and improved ussl

This release brings general improvements and bug fixes to the core and
various ports, as well as documentation additions, clean-ups and better
consistency.  And effort has been made to clean up the source code to
make it more consistent across the core and all ports.

There is a new tool "mpy_bin2res.py" to convert arbitrary (binary) files
to Python resources for inclusion in source code (frozen or otherwise).

The ussl module has seen improvements, including implementation of
server_hostname (for axtls) and server_side mode (for mbedtls).

There is now a double-precision float math library and stmhal has support
to build firmware with software or hardware double-precision.

A detailed list of changes follows.

py core:
- formatfloat: fix number of digits and exponent sign when rounding
- modthread: raise RuntimeError in release() if lock is not acquired
- compile: raise SyntaxError if positional args are given after */**
- objint: support "big" byte-order in int.to_bytes()
- objint: in to_bytes(), allow length arg to be any int and check sign
- compile: fix bug with break/continue in else of optimised for-range
- compile: optimise emitter label indices to save a word of heap
- builtinimport: remove unreachable code for relative imports
- objnamedtuple: simplify and remove use of alloca building namedtuple
- mpprint: remove unreachable check for neg return of mp_format_float
- binary: add missing "break" statements
- runtime: mark m_malloc_fail() as NORETURN
- objstr: remove unnecessary "sign" variable in formatting code
- vm: make "if" control flow more obvious in YIELD_FROM opcode
- modmath: check for zero division in log with 2 args
- makeversionhdr.py: update to parse new release line in docs/conf.py
- objdict: factorise dict accessor helper to reduce code size
- change mp_uint_t to size_t in builtins code
- repl: change mp_uint_t to size_t in repl helpers
- compile: combine arith and bit-shift ops into 1 compile routine
- compile: use switch-case to match token and operator
- objgenerator: allow to hash generators and generator instances
- gc: refactor assertions in gc_free function
- vm: make n_state variable local to just set-up part of VM
- asmx64: support moving a 64-bit immediate to one of top 8 registers
- modmicropython: cast stack_limit value so it prints correctly
- builtinevex: add typechecking of globals/locals args to eval/exec
- py.mk: make berkeley-db C-defs apply only to relevant source files
- mperrno: allow mperrno.h to be correctly included before other hdrs
- mpz: make mpz_is_zero() an inline function
- implement raising a big-int to a negative power
- mkrules.mk: show frozen modules sizes together with executable size
- objtuple: allow to use inplace-multiplication operator on tuples
- objstr: raise an exception for wrong type on RHS of str binary op
- modsys: initial implementation of sys.getsizeof()
- binary.c: fix bug when packing big-endian 'Q' values
- add verbose debug compile-time flag MICROPY_DEBUG_VERBOSE
- binary: change internal bytearray typecode from 0 to 1
- objstringio: prevent offset wraparound for io.BytesIO objects
- objstringio: fix regression with handling SEEK_SET
- stream: seek: Consistently handle negative offset for SEEK_SET
- mkrules.mk: use "find -path" when searching for frozen obj files
- compile: remove unused pn_colon code when compiling func params
- objcomplex: remove unnecessary assignment of variable
- formatfloat: don't post-increment variable that won't be used again
- use "static inline" for funcs that should be inline
- asmthumb: use existing macro to properly clear the D-cache

extmod:
- modussl_axtls: update for axTLS 2.1.3
- modussl_axtls: implement server_hostname arg to wrap_socket()
- move modonewire.c from esp8266 to extmod directory
- modure: if input string is bytes, return bytes results too
- modubinascii: add check for empty buffer passed to hexlify
- modussl_axtls: allow to close ssl stream multiple times
- modussl_mbedtls: support server_side mode
- modussl_mbedtls: when reading and peer wants to close, return 0
- modframebuf: fix invalid stride for odd widths in GS4_HMSB fmt
- modussl_mbedtls: make socket.close() free all TLS resources
- modframebuf: consistently use "col" as name for colour variables
- modussl_mbedtls: implement non-blocking SSL sockets
- machine_signal: fix parsing of invert arg when Pin is first arg
- modframebuf: use correct initialization for .locals_dict
- modlwip: implement setsockopt(IP_ADD_MEMBERSHIP)
- modussl_mbedtls.c: add ussl.getpeercert() method
- modubinascii: rewrite mod_binascii_a2b_base64
- modubinascii: don't post-increment variable that won't be used
- modonewire: rename public module to mp_module_onewire
- for uos.stat interpret st_size member as an unsigned int
- use "static inline" for funcs that should be inline

lib:
- axtls: upgrade to axTLS 2.1.3 + MicroPython patchset
- libm/math: remove implementations of float conversion functions
- add libm_dbl, a double-precision math library, from musl-1.1.16

drivers:
- onewire: move onewire.py, ds18x20.py from esp8266 to drivers
- onewire: enable pull-up when init'ing the 1-wire pin

tools:
- gen-cpydiff: use case description as 3rd-level heading
- pyboard: add license header
- mpy_bin2res: tools to convert binary resources to Python module
- mpy-tool.py: don't generate const_table if it's empty
- mpy-tool.py: fix missing argument in dump() function

tests:
- net_inet/test_tls_sites.py: integration test for SSL connections
- net_inet: add tests for accept and connect in nonblocking mode
- basics: add tests for for-else statement
- net_inet: move tests which don't require full Internet to net_hosted
- connect_nonblock: refactor towards real net_hosted test
- auto detect floating point capabilites of the target
- import: add a test for the builtin __import__ function
- import: update comment now that uPy raises correct exception
- basics/namedtuple1: add test for creating with pos and kw args
- unix/extra_coverage: add test for mp_vprintf with bad fmt spec
- basics: add tests for arithmetic operators precedence
- cpydiff/modules_deque: elaborate workaround
- cpydiff/core_class_mro: move under Classes, add workaround
- cpydiff/core_arguments: move under Functions subsection
- cpydiff/core_class_supermultiple: same cause as core_class_mro
- cpydiff: improve wording, add more workarounds
- cpydiff: add case for str.ljust/rjust
- rename exec1.py to builtin_exec.py
- basics/builtin_exec: test various globals/locals args to exec()

minimal port:
- Makefile: enable gc-sections to remove unused code
- remove unused stmhal include from Makefile
- use size_t for mp_builtin_open argument

unix port:
- modtime: replace strftime() with localtime()
- mpconfigport.mk: update descriptions of readline and TLS options
- Makefile: disable assertions in the standard unix executable
- modjni: convert to mp_rom_map_elem_t
- for uos.stat interpret st_size member as an unsigned int

stmhal port:
- mpconfigport.h: remove config of PY_THREAD_GIL to use default
- make error messages more consistent across peripherals
- add initial implementation of Pin.irq() method
- add .value() method to Switch object, to mirror Pin and Signal
- move pybstdio.c to lib/utils/sys_stdio_mphal.c for common use
- add "quiet timing" enter/exit functions
- make available the _onewire module, for low-level bus control
- modules: provide sym-link to onewire.py driver
- boards/stm32f405.ld: increase FLASH_TEXT to end of 1MiB flash
- sdcard: allow a board to customise the SDIO pins
- add possibility to build with double-precision floating point
- boards: enable double-prec FP on F76x boards
- Makefile: use hardware double-prec FP for MCUs that support it
- Makefile: rename FLOAT_IMPL to MICROPY_FLOAT_IMPL to match C name
- Makefile: add CFLAGS_EXTRA to CFLAGS so cmdline can add options
- mpconfigport.h: allow MICROPY_PY_THREAD to be overridden
- boards: add configuration files for NUCLEO_F429ZI
- boards/NUCLEO_F429ZI: change USB config from HS to FS peripheral
- reduce size of ESPRUINO_PICO build so it fits in flash
- servo: make pyb.Servo(n) map to Pin('Xn') on all MCUs
- servo: don't compile servo code when it's not enabled
- use "static inline" for funcs that should be inline

cc3200 port:
- modusocket: simplify socket.makefile() function
- make non-zero socket timeout work with connect/accept/send
- modusocket: fix connect() when in non-blocking or timeout mode
- use the name MicroPython consistently in code

esp8266 port:
- Makefile: bump axTLS TLS record buffer size to 5K
- Makefile: allow FROZEN_DIR,FROZEN_MPY_DIR to be overridden
- Makefile: add LIB_SRC_C variable to qstr auto-extraction list
- make onewire module and support code usable by other ports
- modonewire: move low-level 1-wire bus code to modonewire.c
- modonewire: make timings static and remove onewire.timings func
- reinstate 1-wire scripts by sym-linking to drivers/onewire/
- move mp_hal_pin_open_drain from esp_mphal.c to machine_pin.c
- enable MICROPY_ENABLE_FINALISER
- README: make "Documentation" a top-level section
- machine_rtc: use correct arithmetic for aligning RTC mem len
- mpconfigport_512k: use terse error messages to get 512k to fit
- mpconfigport.h: make socket a weak link
- modesp: remove unused constants: STA_MODE, etc
- general: add known issue of WiFi RX buffers overflow
- use size_t for mp_builtin_open argument
- fix UART stop bit constants

zephyr port:
- Makefile: rework dependencies and "clean" target
- Makefile: revert prj.conf construction rule to the previous state
- remove long-obsolete machine_ptr_t typedef's
- Makefile: explicitly define default target as "all"
- modusocket: allow to use socketized net_context in upstream
- modusocket: socket, close: switch to native Zephyr socket calls
- modusocket: bind, connect, listen, accept: Swtich to native sockets
- modusocket: send: switch to native sockets
- modusocket: recv: switch to native sockets
- modusocket: fully switch to native Zephyr sockets
- modzephyr: add current_tid() and stacks_analyze() functions
- prj_base.conf: enable CONFIG_INIT_STACKS
- modusocket: update struct sockaddr family field name
- prj_96b_carbon.conf: re-enable networking on Carbon
- modzephyr: add shell_net_iface() function

docs:
- btree: add hints about opening db file and need to flush db
- select: rename to uselect, to match the actual module name
- license: update copyright year
- esp8266/tutorial/intro: discourage use of 512kb firmwares
- esp8266/tutorial/intro: Sphinx requires blank lines around literal blocks
- conf.py: include 3 levels of ToC in latexpdf output
- gc: mark mem_alloc()/mem_free() as uPy-specific
- gc: document gc.threshold() function
- builtins: list builtin exceptions
- conf.py: set default_role = 'any'
- lcd160cr: group related constants together and use full sentences
- ref/speed_python: update and make more hardware-neutral
- library/gc: fix grammar and improve readability of gc.threshold()
- move all ports docs to the single ToC
- topindex.html: remove link to wipy.io, it's no longer available
- conf.py: add .venv dir to exclude_patterns
- move topindex.html to templates/ subdir
- differences/index_template: use consistent heading casing
- builtins: add AssertionError, SyntaxError, ZeroDivisionError
- add glossary
- conf.py: switch to "new" format of intersphinx_mapping
- conf.py: add file for global replacements definition
- library: add CPython docs xref to each pertinent module
- replace.inc: add |see_cpython|, to xref individual symbols from CPython
- conf.py: set "version" and "release" to the same value
- *_index: drop "Indices and tables" pseudo-section
- pyboard: move hardware info into General Info chapter
- uerrno: document "uerrno" module
- esp8266/general.rst: fix name of NTP module
- pyboard: move info about using Windows from topindex to general
- uzlib: update description of decompress() and mention DecompIO
- pyboard/tutorial/amp_skin: add example for playing large WAV files
- library/ubinascii: update base64 docs
- library/usocket: move socket.error to its own section
- library/usocket: describe complete information on address formats
- glossary: elaborate on possible MicroPython port differences
- glossary: fix typos in micropython-lib paragraph
- index: rewrite introduction paragraph to avoid confusion
- use the name MicroPython consistently in documentation
- consistently link to micropython-lib in glossary

all:
- make more use of mp_raise_{msg,TypeError,ValueError} helpers
- unify header guard usage
- remove trailing spaces, per coding conventions
- don't include system errno.h when it's not needed
- use the name MicroPython consistently in comments
- make use of $(TOP) variable in Makefiles, instead of ".."
- raise exceptions via mp_raise_XXX
- make static dicts use mp_rom_map_elem_t type and MP_ROM_xxx macros

README:
- mention support for bytecode and frozen bytecode
- improve description of precompiled bytecode; mention mpy-cross

CODECONVENTIONS:
- clarify MicroPython changes sign-off process
- start to describe docs conventions
- describe docs use of markup for None/True/False

travis:
- build STM32F769DISC board instead of F7DISC to test dbl-prec FP
- pin cpp-coveralls at 0.3.12

Fixes for stmhal USB mass storage, lwIP bindings and VFS regressions

This release provides an important fix for the USB mass storage device in
the stmhal port by implementing the SCSI SYNCHRONIZE_CACHE command, which
is now require by some Operating Systems.  There are also fixes for the
lwIP bindings to improve non-blocking sockets and error codes.  The VFS has
some regressions fixed including the ability to statvfs the root.

All changes are listed below.

py core:
- modbuiltins: add core-provided version of input() function
- objstr: catch case of negative "maxsplit" arg to str.rsplit()
- persistentcode: allow to compile with complex numbers disabled
- objstr: allow to compile with obj-repr D, and unicode disabled
- modsys: allow to compile with obj-repr D and PY_ATTRTUPLE disabled
- provide mp_decode_uint_skip() to help reduce stack usage
- makeqstrdefs.py: make script run correctly with Python 2.6
- objstringio: if created from immutable object, follow copy on write policy

extmod:
- modlwip: connect: for non-blocking mode, return EINPROGRESS
- modlwip: fix error codes for duplicate calls to connect()
- modlwip: accept: fix error code for non-blocking mode
- vfs: allow to statvfs the root directory
- vfs: allow "buffering" and "encoding" args to VFS's open()
- modframebuf: fix signed/unsigned comparison pendantic warning

lib:
- libm: use isfinite instead of finitef, for C99 compatibility
- utils/interrupt_char: remove support for KBD_EXCEPTION disabled

tests:
- basics/string_rsplit: add tests for negative "maxsplit" argument
- float: convert "sys.exit()" to "raise SystemExit"
- float/builtin_float_minmax: PEP8 fixes
- basics: convert "sys.exit()" to "raise SystemExit"
- convert remaining "sys.exit()" to "raise SystemExit"

unix port:
- convert to use core-provided version of built-in import()
- Makefile: replace references to make with $(MAKE)

windows port:
- convert to use core-provided version of built-in import()

qemu-arm port:
- Makefile: adjust object-file lists to get correct dependencies
- enable micropython.mem_*() functions to allow more tests

stmhal port:
- boards: enable DAC for NUCLEO_F767ZI board
- add support for NUCLEO_F446RE board
- pass USB handler as parameter to allow more than one USB handler
- usb: use local USB handler variable in Start-of-Frame handler
- usb: make state for USB device private to top-level USB driver
- usbdev: for MSC implement SCSI SYNCHRONIZE_CACHE command
- convert from using stmhal's input() to core provided version

cc3200 port:
- convert from using stmhal's input() to core provided version

teensy port:
- convert from using stmhal's input() to core provided version

esp8266 port:
- Makefile: replace references to make with $(MAKE)
- Makefile: add clean-modules target
- convert from using stmhal's input() to core provided version

zephyr port:
- modusocket: getaddrinfo: Fix mp_obj_len() usage
- define MICROPY_PY_SYS_PLATFORM (to "zephyr")
- machine_pin: use native Zephyr types for Zephyr API calls

docs:
- machine.Pin: remove out_value() method
- machine.Pin: add on() and off() methods
- esp8266: consistently replace Pin.high/low methods with .on/off
- esp8266/quickref: polish Pin.on()/off() examples
- network: move confusingly-named cc3200 Server class to its reference
- uos: deconditionalize, remove minor port-specific details
- uos: move cc3200 port legacy VFS mounting functions to its ref doc
- machine: sort machine classes in logical order, not alphabetically
- network: first step to describe standard network class interface

examples:
- embedding: use core-provided KeyboardInterrupt object