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Bluepad32 firmware for AirLift

What is AirLift

AirLift is an ESP32 module. This module is a "co-processor", usually used to bring WiFi or BLE to the main processor.

AirLift modules are present in some Adafruit boards, like in:

Or it can be a standalone board:

AirLift modules come pre-installed with Adafruit's NINA firmware.

NOTE: Adafruit's NINA firmware is a fork of Arduino's NINA firmware. They are pretty similar, but they are not compatible since they use different SPI pins.

In order to have gamepad support, the original AirLift firmware must be replaced with Bluepad32 firmware. This is a simple step that needs to be done just once, and can be "undone" at any time.

how-does-it-work

This is how it works:

  • Gamepad (A) talks to AirLift module (B)
  • AirLift module (B) talks to main processor (C)

Bluepad32 firmware is "compatible-enough" with the original firmware:

  • Uses SPI, and the same GPIOs to talk to the main processor
  • Uses the same protocol that runs on top of SPI
  • But not all messages are implemented. Only the ones that are needed to have gamepad support working.

Flashing Bluepad32 firwmare

To flash Bluepad32 firmware, you have to:

  1. Put the Adafruit board in "pass-through" mode
  2. Flash pre-compiled version
  3. Or compile it yourself and flash it.

1. Put Adafruit board in "passthrough" mode

Might slightly vary from board to board, but basically what you have to do is:

  1. Put the board in "boot" mode, usually by double pressing the "reset" button.
  2. Flash the right "Passthrough" firmware for your board.

2. Flash pre-compiled version

Download latest pre-compiled version from here:

Unzip it, and follow the instructions described in the README.md file.

3. Or compile it yourself and flash it

Install the requirements described here: README.md.

Chose airlift as the target platform:

cd {BLUEPAD32}/src/

# Select AirLift platform:
# Components config -> Bluepad32 -> Target Platform -> AirLift
idf.py menuconfig

# And then compile it!
idf.py build

To flash it, you have to use the --before no_reset option:

# Flash it!

# Port might be different
export ESPPORT=/dev/ttyACM0

esptool.py --port ${ESPPORT} --baud 115200 --before no_reset write_flash 0x1000 ./build/bootloader/bootloader.bin 0x10000 ./build/bluepad32-airlift.bin 0x8000 ./build/partitions_singleapp.bin

CircuitPython example

The Bluepad32 library for CircuitPython, including a working example is available here:

How to debug Bluepad32 for AirLift

ADVANCED: Normally you wouldn't need this.

Assuming that the ESP32 UART pins are not exposed (true for all AirLift modules), the recommended way to debug the Bluepad32 firmware is:

ESP32 SAMD51
MOSI 14 MOSI
MISO 23 MISO
SCK 18 SCK
CS 5 D10
READY 33 D9
RESET EN D6

Something like this (left: Feather M4 express, right: HUZZAH32)

fritzing

NOTE: If you use a HUZZAH32, pay attention to the GPIO labels. The MOSI/MISO/SCK lables that are in the front of board, are not the ones that you should use. See the back of the board for the correct GPIO numbers.

In real life it might look more messy:

wiring

The benefits of using two separate modules (SAMD51 + ESP32) are:

  • You can see the console of both the ESP32 and SAM51 at the same time
  • Faster flashing: it is > 2x faster to flash Bluepad32 directly to the ESP32 than to flash it with "PassThrough" method required for AirLift modules.
  • If needed, you can inspect the SPI protocol with a logic analizer