MCP2221 pins driven low during import of board

[Rainerlan]

I try to control shutters. Their movement is being triggered by a LOW input signal. Hence, the shutter-input MUST stay high (unless commanded to move otherwise). I connected G0 (later configured as OUTPUT) to the shutter input pin.

Without a pullup at G0, when executing "import board" in python3, G0 pin is being pulled to ground several times. After attaching a pullup (100kOhm) at G0, still after executing "import board", G0 pin is being pulled to ground for ~12ms.

Note: This is before digitalio is being imported and before the pins are being setup as OUTPUT. How can I avoid G0 being pulled to low during startup of the script (import of board)?

[caternuson]

Try suppressing the software reset by setting the environment variable MCP2221_RESET_DELAY to 0. Exactly how to do that is OS dependent. But it'd be the same way you are setting BLINKA_MCP2221 to 1.

[caternuson]

Although the pins are also set to inputs at startup: https://github.com/adafruit/Adafruit_Blinka/blob/802e6874ffa75449f61e229e7aeb00fc5e0022ab/src/adafruit_blinka/microcontroller/mcp2221/mcp2221.py#L64-L66

[Rainerlan]

export BLINKA_MCP2221_RESET_DELAY=-1 does skip the reset - and hence does NOT change the pins output states, which is great!

Second problem was, that changing the direction to OUTPUT, the pins got low. This had to be changed in the code:

https://github.com/adafruit/Adafruit_Blinka/blob/802e6874ffa75449f61e229e7aeb00fc5e0022ab/src/adafruit_blinka/microcontroller/mcp2221/mcp2221.py#L160

to report = bytearray(b"\x50" + b"\x01" * 17 + b"\x00" * 46) # empty set GPIO report

Also I removed the lines 64-66 https://github.com/adafruit/Adafruit_Blinka/blob/802e6874ffa75449f61e229e7aeb00fc5e0022ab/src/adafruit_blinka/microcontroller/mcp2221/mcp2221.py#L64-L66 Don't know why the pins shall be set to GPIs when not explicitly requested...

[Rainerlan]

After applying the above changes, the GPIOs work as I need them to work (default set to HIGH/3.3V when changing them to outputs - also the reset is not messing around with the pins output states)

[caternuson]

Oops, sry, meant negative number for the reset envar.

Good hacks for the other parts! Glad you got it working.

[Rainerlan]

@caternuson Thanks a lot for your support!