I’m hacking on adding Arduino Zero support to the Zephyr Project at the
moment. I had a look at speeding up
crc16_ccitt() but ran into a
problem: there’s so many variants of CRC16-CCITT to choose from!
Zephyr uses CRC-16/AUG-CCITT which is equivalent to CRC-16/CCITT-FALSE with two zero bytes prepended. The effective seed is
0x1d0fand test vector output is
Mynewt uses CRC-16/XMODEM. The seed is 0 and test vector output is
Contiki uses CRC-16/CCITT. The seed is 0, input and output are bit reversed, and test vector output is
Linux uses CRC-16/MCRF4XX. The seed is
0xffff, input and output are bit reversed, and the test vector output is
The Arduino Zero’s SAMD21 uses CRC-16/CCITT as per Contiki.
Contiki, Linux, and the SAMD21 are the same except for the seed. Zephyr is close, but you need to modify the seed to account for the padding. Mynewt is the outlier as all others reverse the input and output.
See http://reveng.sourceforge.net/crc-catalogue/16.htm for a catalogue.