Lightly tested:
* no matches (catch-all)
* standard address single address matches (even and odd positions)
* standard address mask matches
* only tested that extended doesn't match non-extended
Tested & working:
* Send standard packets
* Receive standard packets (1 FIFO, no filter)
Interoperation between SAM E54 Xplained running this tree and
MicroPython running on STM32F405 Feather with an external
transceiver was also tested.
Many other aspects of a full implementation are not yet present,
such as error detection and recovery.
Jeff Epler