Module crc 

CRC-16 as used by the ATECC608B protocol.

Parameters of the algorithm (Microchip uses the name “CRC-16/DNP” loosely. The chip’s variant matches none of the standard catalog entries exactly, the parameters below are the source of truth):

• Polynomial : 0x8005
• Initial value : 0x0000
• Reflect input : false (MSB first)
• Reflect output: false
• XOR output : 0x0000
• Byte order : low byte first when serialized on the wire

The implementation is a faithful translation of the bit-by-bit routine in lib/calib/calib_command.c of Microchip’s CryptoAuthLib. We deliberately avoid a table-driven approach. The driver only computes a CRC over short packets at human time scales (microseconds), so the gain would be negligible while flash usage would grow.

Functions

crc16

Compute the CRC-16 over data.

crc16_to_bytes

Serialize a CRC into the two-byte little-endian form expected on the wire.

verify_trailing_crc 🔒

Verify the trailing two bytes of frame against a freshly computed CRC of everything before them.