raspberrypi: rare hard locks when writing flash while RGBMatrix is active

[jepler]

I spent much of the weekend developing a project on the Feather RP2040 that uses RGBMatrix.

Occasionally (1 in 20?) times when I would write out code.py, the board would freeze (USB stopped, matrix scanning stopped). A hard reset cured it, and I never lost my CIRCUITPY contents.

@ladyada also saw this at least once while she was testing the code, but we decided at the time to brush it off. Unfortunately, it's real and it's still there.

[daveythacher]

Can you post code?

[jepler]

There's no code per se, because it locks up during disk activity and/or soft reload. I assume that the code from the guide will set up the conditions for eventual failure:

displayio.release_displays()
matrix = rgbmatrix.RGBMatrix(
    width=64, bit_depth=4,
    rgb_pins=[board.D6, board.D5, board.D9, board.D11, board.D10, board.D12],
    addr_pins=[board.D25, board.D24, board.A3, board.A2],
    clock_pin=board.D13, latch_pin=board.D0, output_enable_pin=board.D1)
display = framebufferio.FramebufferDisplay(matrix)

In my specific case, I would be repeatedly editing & saving a ~8kB (240 line) code file using vim on a raspberry pi 4 as the host computer.