crc.h File Reference

Parameterized CRC engine - one source of truth for every cyclic redundancy check. More...

#include "protocore_config.h"

Go to the source code of this file.

Classes
struct	protocore_crc_params
	One CRC's full definition (Rocksoft model). See the file comment. More...
struct	CrcArgs
	What one CRC step runs over: the definition, the running register, and the octets. More...
struct	CrcVars
struct	CrcNs
	The entries. More...

Functions
void	protocore_crc_begin (uint8_t *work)
void	protocore_crc_update (uint8_t *work)
void	protocore_crc_final (uint8_t *work)
void	protocore_crc_compute (uint8_t *work)

Variables
CrcVars	CrcV
	The operands and the outcome.
const protocore_crc_params	PROTOCORE_CRC8_SMBUS
	CRC-8/SMBUS (a.k.a. CRC-8). check = 0xF4.
const protocore_crc_params	PROTOCORE_CRC8_MAXIM_DOW
	CRC-8/MAXIM-DOW (1-Wire / Dallas). check = 0xA1.
const protocore_crc_params	PROTOCORE_CRC8_NRSC5
	CRC-8/NRSC-5 - the sensor CRC. check = 0xF7. Used by services/sht3x.
const protocore_crc_params	PROTOCORE_CRC16_ARC
	CRC-16/ARC (a.k.a. CRC-16, IBM). check = 0xBB3D.
const protocore_crc_params	PROTOCORE_CRC16_MODBUS
	CRC-16/MODBUS. check = 0x4B37.
const protocore_crc_params	PROTOCORE_CRC16_IBM_3740
	CRC-16/IBM-3740 (often called CCITT-FALSE). check = 0x29B1.
const protocore_crc_params	PROTOCORE_CRC16_XMODEM
	CRC-16/XMODEM. check = 0x31C3.
const protocore_crc_params	PROTOCORE_CRC16_KERMIT
	CRC-16/KERMIT (a.k.a. CRC-16/CCITT, reflected). check = 0x2189.
const protocore_crc_params	PROTOCORE_CRC16_X25
	CRC-16/X-25 (HDLC FCS). check = 0x906E. Used by services/radio/thread, mbplus, nema_ts2.
const protocore_crc_params	PROTOCORE_CRC16_DNP
	CRC-16/DNP (DNP3 link-layer block check). check = 0xEA82. Used by services/dnp3.
const protocore_crc_params	PROTOCORE_CRC24_OPENPGP
	CRC-24/OPENPGP. check = 0x21CF02.
const protocore_crc_params	PROTOCORE_CRC32_ISO_HDLC
	CRC-32/ISO-HDLC (zlib / PKZIP / Ethernet). check = 0xCBF43926.
const protocore_crc_params	PROTOCORE_CRC32_BZIP2
	CRC-32/BZIP2 (unreflected CRC-32). check = 0xFC891918.

Detailed Description

Parameterized CRC engine - one source of truth for every cyclic redundancy check.

One implementation for every CRC in the tree: C37.118, DF1, DNP3, EnOcean, INTERBUS, Modbus, Modbus Plus, NEMA TS2, raw L2, SDI-12, SHT3x, Thread and Zigbee all checksum through it. Three checks stay outside it: the WAL is table-driven for bulk log throughput, RTCM3's CRC-24Q has no preset here, and DShot's "CRC" is a 4-bit XOR fold rather than a CRC at all.

It is the standard Rocksoft / Williams model, so any published CRC is expressible as six numbers and needs no new code:

• protocore_crc_params::width register width in bits (8..32)
• protocore_crc_params::poly generator polynomial, normal form, implicit top bit dropped
• protocore_crc_params::init initial register value
• protocore_crc_params::refin reflect each input octet
• protocore_crc_params::refout reflect the final register
• protocore_crc_params::xorout final XOR

Every preset below carries its catalogue check value - the CRC of the nine ASCII octets "123456789" - and test_crc asserts each one: a wrong polynomial or a flipped reflect flag cannot reproduce a published check value by accident.

Bitwise, not table-driven: a 256-entry table per polynomial would cost more flash than the frames are worth on this class of device, and every caller here checksums tens to hundreds of octets, not megabytes. Pure, so it is host-testable and identical on device and host.

Author

Douglas Quigg (dstroy0)

Date

2026

Definition in file crc.h.

Function Documentation

protocore_crc_begin()

void protocore_crc_begin

(

uint8_t *

work

)

protocore_crc_update()

void protocore_crc_update

(

uint8_t *

work

)

protocore_crc_final()

void protocore_crc_final

(

uint8_t *

work

)

protocore_crc_compute()

void protocore_crc_compute

(

uint8_t *

work

)

Variable Documentation

CrcV

CrcVars CrcV

extern

The operands and the outcome.

PROTOCORE_CRC8_SMBUS

const protocore_crc_params PROTOCORE_CRC8_SMBUS

extern

CRC-8/SMBUS (a.k.a. CRC-8). check = 0xF4.

PROTOCORE_CRC8_MAXIM_DOW

const protocore_crc_params PROTOCORE_CRC8_MAXIM_DOW

extern

CRC-8/MAXIM-DOW (1-Wire / Dallas). check = 0xA1.

PROTOCORE_CRC8_NRSC5

const protocore_crc_params PROTOCORE_CRC8_NRSC5

extern

CRC-8/NRSC-5 - the sensor CRC. check = 0xF7. Used by services/sht3x.

PROTOCORE_CRC16_ARC

const protocore_crc_params PROTOCORE_CRC16_ARC

extern

CRC-16/ARC (a.k.a. CRC-16, IBM). check = 0xBB3D.

PROTOCORE_CRC16_MODBUS

const protocore_crc_params PROTOCORE_CRC16_MODBUS

extern

CRC-16/MODBUS. check = 0x4B37.

PROTOCORE_CRC16_IBM_3740

const protocore_crc_params PROTOCORE_CRC16_IBM_3740

extern

CRC-16/IBM-3740 (often called CCITT-FALSE). check = 0x29B1.

PROTOCORE_CRC16_XMODEM

const protocore_crc_params PROTOCORE_CRC16_XMODEM

extern

CRC-16/XMODEM. check = 0x31C3.

PROTOCORE_CRC16_KERMIT

const protocore_crc_params PROTOCORE_CRC16_KERMIT

extern

CRC-16/KERMIT (a.k.a. CRC-16/CCITT, reflected). check = 0x2189.

PROTOCORE_CRC16_X25

const protocore_crc_params PROTOCORE_CRC16_X25

extern

CRC-16/X-25 (HDLC FCS). check = 0x906E. Used by services/radio/thread, mbplus, nema_ts2.

PROTOCORE_CRC16_DNP

const protocore_crc_params PROTOCORE_CRC16_DNP

extern

CRC-16/DNP (DNP3 link-layer block check). check = 0xEA82. Used by services/dnp3.

PROTOCORE_CRC24_OPENPGP

const protocore_crc_params PROTOCORE_CRC24_OPENPGP

extern

CRC-24/OPENPGP. check = 0x21CF02.

PROTOCORE_CRC32_ISO_HDLC

const protocore_crc_params PROTOCORE_CRC32_ISO_HDLC

extern

CRC-32/ISO-HDLC (zlib / PKZIP / Ethernet). check = 0xCBF43926.

PROTOCORE_CRC32_BZIP2

const protocore_crc_params PROTOCORE_CRC32_BZIP2

extern

CRC-32/BZIP2 (unreflected CRC-32). check = 0xFC891918.