Module crc 

Modbus CRC-16 and LRC checksum functions.

• CRC-16/MODBUS: Used by Modbus RTU frames. Polynomial 0xA001 (reflected), init 0xFFFF, no final XOR.
• LRC: Longitudinal Redundancy Check used by Modbus ASCII frames. Two’s complement of the sum of all bytes (mod 256).

Functions

modbus_crc16

Compute the Modbus CRC-16 checksum.

modbus_lrc

Compute the Modbus LRC (Longitudinal Redundancy Check).

verify_crc16

Verify the CRC-16 of a complete Modbus RTU frame (data + 2-byte CRC).

verify_lrc

Verify the LRC of a data slice where the last byte is the LRC.