stm32: Meowbit board.MENU button can't be used — pin in use error

[deshipu]

CircuitPython version

Adafruit CircuitPython 7.0.0-beta.0-123-g89fc1890a-dirty on 2021-08-30; MEOWBIT with STM32F401xE

Code/REPL

>>> import board
>>> import digitalio
>>> digitalio.DigitalInOut(board.MENU)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: MENU in use

Behavior

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: MENU in use

Description

No response

Additional information

The board.MENU seems to be PC15. I couldn't find any references to that pin in board.c, so I guess something is wrong with the code that checks whether the pin is in use or not?

[dhalbert]

circuitpython/ports/stm/peripherals/stm32f4/stm32f401xe/gpio.c

Line 41 in 0ee0ed7

never_reset_pin_number(2,15); // PC15 OSC32_OUT

says PC15 is OSC32_OUT, and so reserves it. There is no public schematic for the Meowbit, so I'm not sure if OSC32 is used or not, and would even be available after boot.

[deshipu]

Perhaps the pin for the menu button is wrong then.

Looking at https://www.kittenbot.cc/collections/frontpage/products/meowbit-codable-console-for-microsoft-makecode-arcade that button also enables DFU mode. I'm looking at the datasheet for STM32F401RET6 and the bootloader docs, but I can't see any reference to what pin that might be.

The micropython fork at https://github.com/KittenBot/micropython_meowbit simply doesn't define a menu pin at all.

Perhaps @KittenBot could comment on this?

[deshipu]

Looking at the PCB traces under a microscope, it looks like the MENU button is indeed connected to pin PC15.