Generic F411CEUx digitalPinToPinName() bug

[dfleck]

It seems digitalPinToPinName() is slightly broken on Generic F411CEUx. Version 2.11.0 on Arduino 2.3.5 on Mac.

Also on BlackPill FC411CE

Serial.println(PB_13_ALT1); returns 285
Serial.println(digitalPinToPinName(PB_13_ALT1)); returns 286

Discovered the problem trying to do:
SPIClass SPI_4(PA1, PA11, PB_13_ALT1);

[fpistm]

No issue here. You just not use correct syntax.
This is not PB_13_ALT1 but PB13_ALT1.

[dfleck]

So the problem is not in digitalPinToPinName() but must be somewhere in the pin definitions. Investigating further:

In variants/STM32F4xx/F411C(C-E)(U-Y)/PinNamesVar.h
PB_13_ALT1 = PB_13 | ALT1, so PB_13_ALT1 is a valid syntax

Serial.println(PB_13_ALT1); prints 285
Serial.println(PB13_ALT1); prints 284
Serial.println(PB_13 | ALT1); prints 285
Serial.println(PB_13); I think should be 28 but it prints 29

Could it be off-by-one because there's no PB_11 in the const PinName digitalPin[] = { table in variants/STM32F4xx/F411C(C-E)(U-Y)/variant_generic.cpp?

[fpistm]

PB_13_ALT1 = PB_13 | ALT1, so PB_13_ALT1 is a valid syntax

Yes it is a valid syntax but you mixed type between pin number (PYn) and PinName (PY_n), they are not the same.
All Arduino API uses pin number PYn. It is an alias to ease use of STM32.
In your case with generic F411CEUx:
PB13 is a pin number with value 28. It is used as index to find the PinName PB_13 in the digitalPin array.
So PB_13 is equal to PB_13 = (PortB << 4) + 0x0D with PortB = 0x01 then PB_13 = 0x1D = 29
ALT1 = 0x100.
So no issue here you only mix type.
digitalWrite(PB13) or digitalWrite(28) or digitalWrite(D28)is correct but digitalWrite(PB_13) is not correct as you will write in fact to pin number 29 digitalWrite(29) which is PB14.

[dfleck]

Thanks you so much much for explaining this. I was definitely confused about the different types.