The pinPeripheral() function in wiring_private.c has support for "PIO_INPUT", "PIO_INPUT_PULLUP" and "PIO_OUTPUT". It lacks support for the "PULL DOWN" configuration.

Interestingly, pinMode() does support "INPUT_PULLDOWN".

I propose that we add:

 if ( ulPeripheral == PIO_INPUT_PULLDOWN )
 {
 pinMode( ulPin, INPUT_PULLDOWN ) ;
 }

We will also need to add PIO_INPUT_PULLDOWN to the EPioType in WVariant.h.

I would be happy to submit a PR for this. Before I do, I have one question regarding suggestions of how best to set up my environment to use the ArduinoCore-samd Git repo instead of the core that is installed with the IDE.