Porting micropython to STM32Nucleo-F4

[dhylands]

I happen to have a 401NUCLEO board sitting on my shelf, so I cloned your repository and flashed using stlink.

I was able to reproduce your results. I tried A0 thru A10 (skipping A2/A3 since those are are REPL UART) and on all of them except A9, the pullup seemed to work fine.

Since A9 is used for VBUS sensing, I theorized that some USB circuitry was being connected.
I modified your mpconfigbord.h file and commented out the

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#define MICROPY_HW_USB_VBUS_DETECT_PIN (pin_A9)

line, but that didn't seem to make any difference.

You may need to completely disable the USB device completely (which IIRC is non-trivial with the current codebase) in order to get the internal A9 pullup to behave properly.

[mike38]

thanks a lot for your tests. Now I know it is not a mistake or a hardware failure.

I will add an external pull up or modify my circuit to not use A9.