I [might be possible](https://www.microchip.com/wwwproducts/en/ATSAMC20E18A) that you can use my [SAMD21 grblHAL driver](https://github.com/terjeio/grblHAL/tree/master/drivers/SAMD21) either as-is or as a basis for a grbl port. Good luck!
I might be possible that you can use my SAMD21 grblHAL driver either as-is or as a basis for a grbl port.
Good luck!