unwritten.md

Unwritten topics

• More debugging patterns: breakpoints, watchpoints, bkpt, etc.
• The .data and .bss sections: static variables, linker script (again) and initialization routine.
• Guaranteed panic!-free programs with this one weird trick!
• The Rust allocator interface.
• Debug prints with ITM (Instrumentation Trace Macrocell)
• "Apps"
  • Heartbeat LED
  • Read an analog sensor. e.g. just potentiometer, a photoresistor or a CNY70.
  • Read a digital sensor via SPI or I2C. e.g. motion sensor.
  • Data acquisition. e.g. sensor + serial comm
  • Move a servomotor
  • Open loop control system. e.g. serial comm + servo or potentiometer + servo
  • Closed loop control system. e.g. servo + magnetometer
• Interfacing external devices
  • Buttons and debouncing.
  • Servomotors.
• Async and concurrency
  • Scheduling strategies: Super loop, cooperative, preemptive.
  • Interrupts: asm!("cpsid i"), asm!("cpsie i"), data races and atomic operations.
  • DMA
• FPU
• nm -C --size-sort: binary size profiling
• nm -C: global vs local text symbol
• librarify: src/lib.rs + src/bin/*.rs. Uses extern (lib) and no_mangle (bin) symbol. Basically the library says: you (the binary) must give me a symbol with this unmangled name. Downside: types signatures are lost. How to recover them? traits? Related: weak symbols for e.g. exceptions.
• ARM calling convention:
  • cf. http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042f/IHI0042F_aapcs.pdf
  • A diagram of how the stack, the heap and static variables (.data, .bss) are allocated in RAM.
  • An explanation of how the call stack works: stack pointer, stack frames, what happens when a function/interrupt is called, etc.
  • How arguments are passed to functions: via stack, registers
• mention that a section can't exceed its region capacity. This is automatically enforced by the linker based on what the linker script says.
• bluetooth: HC-06. rfcomm bind rfcomm0 $ADDRESS
• document other flashing methods: ELF -> objcopy -> binary, then directly flash the binary using OpenOCD (without gdb) or st-link.
• revisit the default exception handler: where did we come from? (inspect stack) which exception is this? (inspect NVIC(?) register).
  • cf. http://www.freertos.org/Debugging-Hard-Faults-On-Cortex-M-Microcontrollers.html
• embedding Rust in C frameworks like FreeRTOS or the Photon.
  • cf. https://github.com/japaric/photon