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Extend the Micropython Firmware

If you want to "freeze" a python module to free up RAM, or if you want to extend any of the frozen/native modules TMC or MCPWM, you'll need to re-compile the firmware.

The process is fully described in the esp32 port's README.md, but is mostly already taken care of. Start by initializing this repo's submodules:

$ git submodule update --init --recursive

This clones the nested repos at /firmware/frameworks/, which are the following projects:

Micropython

The referenced micropython fork supports the ESP32's MCPWM-Module, standing for Motor control Pulse-Width-Modulation. This was required to have enough PWM outputs available (6 modules).
Read more about the MCPWM in Espressif's API documentation!

ESP-IDF

For better MCPWM-frequency update behaviour, we use a minimally modified variant of the esp-idf, v3.3.1.

The Micropython ESP32 port's Makefile located at firmware/frameworks/micropython/ports/esp32 should already have the correct commit referenced, which was checked out while initializing the submodules:

...
# The git hash of the currently supported ESP IDF version.
# These correspond to v3.3.1 and v4.0.
ESPIDF_SUPHASH_V3 := cc02b01ea59e112e6ccf7fc3b66f3624f5d41167  # patched MCPWM update behaviour, based upon v3.3.1
ESPIDF_SUPHASH_V4 := 463a9d8b7f9af8205222b80707f9bdbba7c530e1
...

Frozen Modules

The last puzzle piece is the stepper-driver specific python package tmc_control, located at firmware/src_frozen.

Since it contains mappings for almost all of TMC2130's registers, this uses up a ton of RAM if loaded dynamically. Therefore, they are better "frozen" into the Micropython firmware.

This is achieved by copying the modules from /firmware/src_frozen to /firmware/frameworks/micropython/ports/esp32/modules:

  • tmc_control
    • init.py
    • axis.py
    • tmc2130.py
  • uasyncio
    • init.py
    • core.py
  • uftpd.py

(Actually, the latter two, uasyncio and uftpd should already be there.)

Configuration

The remaining steps are explained in more detail in ports/esp32/README.me.

The environment variables for the build process are defined in GNUMakefile, which takes precedence over Makefile:

ESPIDF = ../../../esp-idf
BOARD = GENERIC
PORT = /dev/tty.usbserial-DN05LWXG
FLASH_MODE = dio
FLASH_SIZE = 4MB
CROSS_COMPILE = $(ESPIDF)/xtensa-esp32-elf/bin/xtensa-esp32-elf-

include Makefile

Make sure to adjust the PORT according to your setup!

Compiling

See the esp32 port's README.md for troubleshooting.

$ cd mpy-cross
$ make mpy-cross

$ cd ../ports/esp32
$ make clean
$ make submodules
$ make deploy # erases the ESP32's firmware and uploads!