Thanks Martin. I am not sure why the Te pin has to be on SERCOM3. The data sheet says all SERCOMs support RS485 and the Itsy is already using SERCOM1 for Tx and Rx then I should be able to use SERCOM1 pad2 for Te, yes? Page 854 of the data sheet.
SERCOM3 pad2 (pin33) is being used by the USB data on the Itsy board.
Is this:
PORT->Group[g_APinDescription[10].ulPort].PINCFG[g_APinDescription[10].ulPin].bit.PMUXEN = 1;
arduino code?
SERCOM5 on the Feather M4 has the Tx/Tx pins and SERCOM3 is the USB
SERCOM1 on the Itsy M4 has the Tx/Rx pins and SERCOM3 is the USB