Metro M4 Express additional UART handling incorrect

[rce1086]

Metro M4 Express

UART on pins 0/1 used for serial LCD display: attempting to create an additional UART (needed because of no raw serial stream being available from host PC via USB) on pins D10,D11 (as indicated by the example script as a usable pair) ascom = busio.UART( board.D10, board.D11, baudrate=9600, bits=8, parity=None, stop=1, timeout=0.25, receiver_buffer_size=64) doesn't work - reception on D11 is OK, but nothing gets send on D10 (as shown by logic analyser on pins); experimenting with other pins (using D13 for TX, for example, with RX on D11) does work, as do A4/A5, suggesting that only pad0 can successfully be used for TX The CircuitPython sources are written to assign either pad0 or pad1 (via a division on TXPO), but it appears that only pad0 assignments work...

[ladyada]

thats correct, on SAMD51/M4 boards TX can only be pad 0, RX can be any pin

[rce1086]

Thanks for confirming this, Lady Ada. May I request, therefore, that the CircuitPython code https://github.com/adafruit/circuitpython/blob/master/ports/atmel-samd/common-hal/busio/UART.c around line 91+4 be tightened up to reject these inappropriate settings, rather than setting configurations which won't work, thus making the output of the sample script https://github.com/adafruit/Adafruit_Learning_System_Guides/blob/master/CircuitPython_Essentials/UART_Test_Script.py reflect reality... Thanks to all involved, I'm liking CircuitPython :-)

[ladyada]

yep we'll look at it - thanks for the bug report :)

[tannewt]

@rce1086 Would you like to take a stab at fixing this? You found the right place. That test needs an ifdef to correct it for SAMD51 similar to what is done here: https://github.com/adafruit/circuitpython/blob/master/ports/atmel-samd/common-hal/audioio/AudioOut.c#L124

[rce1086]

Sorry for the delay in replying: yes, I will - I assume you're looking for a pull request?

[tannewt]

Yes please!

[tannewt]

Fixed in #1989. Thank you!