CRC

Enumerations
enum	crc_type {   CRC4 , CRC4_TI , CRC7_BE , CRC8 ,   CRC8_CCITT , CRC16 , CRC16_ANSI , CRC16_CCITT ,   CRC16_ITU_T , CRC32_C , CRC32_IEEE }
	CRC algorithm enumeration. More...

Functions
uint16_t	crc16 (uint16_t poly, uint16_t seed, const uint8_t *src, size_t len)
	Generic function for computing a CRC-16 without input or output reflection.
uint16_t	crc16_reflect (uint16_t poly, uint16_t seed, const uint8_t *src, size_t len)
	Generic function for computing a CRC-16 with input and output reflection.
uint8_t	crc8 (const uint8_t *src, size_t len, uint8_t polynomial, uint8_t initial_value, bool reversed)
	Generic function for computing CRC 8.
uint16_t	crc16_ccitt (uint16_t seed, const uint8_t *src, size_t len)
	Compute the checksum of a buffer with polynomial 0x1021, reflecting input and output.
uint16_t	crc16_itu_t (uint16_t seed, const uint8_t *src, size_t len)
	Compute the checksum of a buffer with polynomial 0x1021, no reflection of input or output.
static uint16_t	crc16_ansi (const uint8_t *src, size_t len)
	Compute the ANSI (or Modbus) variant of CRC-16.
uint32_t	crc32_ieee (const uint8_t *data, size_t len)
	Generate IEEE conform CRC32 checksum.
uint32_t	crc32_ieee_update (uint32_t crc, const uint8_t *data, size_t len)
	Update an IEEE conforming CRC32 checksum.
uint32_t	crc32_c (uint32_t crc, const uint8_t *data, size_t len, bool first_pkt, bool last_pkt)
	Calculate CRC32C (Castagnoli) checksum.
uint8_t	crc8_ccitt (uint8_t initial_value, const void *buf, size_t len)
	Compute CCITT variant of CRC 8.
uint8_t	crc7_be (uint8_t seed, const uint8_t *src, size_t len)
	Compute the CRC-7 checksum of a buffer.
uint8_t	crc4_ti (uint8_t seed, const uint8_t *src, size_t len)
	Compute the CRC-4 checksum of a buffer.
uint8_t	crc4 (const uint8_t *src, size_t len, uint8_t polynomial, uint8_t initial_value, bool reversed)
	Generic function for computing CRC 4.
static uint32_t	crc_by_type (enum crc_type type, const uint8_t *src, size_t len, uint32_t seed, uint32_t poly, bool reflect, bool first, bool last)
	Compute a CRC checksum, in a generic way.

Detailed Description

Enumeration Type Documentation

crc_type

enum crc_type

#include <zephyr/sys/crc.h>

CRC algorithm enumeration.

These values should be used with the CRC dispatch function.

Enumerator
CRC4	Use crc4.
CRC4_TI	Use crc4_ti.
CRC7_BE	Use crc7_be.
CRC8	Use crc8.
CRC8_CCITT	Use crc8_ccitt.
CRC16	Use crc16.
CRC16_ANSI	Use crc16_ansi.
CRC16_CCITT	Use crc16_ccitt.
CRC16_ITU_T	Use crc16_itu_t.
CRC32_C	Use crc32_c.
CRC32_IEEE	Use crc32_ieee.

Function Documentation

crc16()

uint16_t crc16	(	uint16_t	poly,
		uint16_t	seed,
		const uint8_t *	src,
		size_t	len
	)

#include <zephyr/sys/crc.h>

Generic function for computing a CRC-16 without input or output reflection.

Compute CRC-16 by passing in the address of the input, the input length and polynomial used in addition to the initial value. This is O(n*8) where n is the length of the buffer provided. No reflection is performed.

Note

If you are planning to use a CRC based on poly 0x1012 the functions crc16_itu_t() is faster and thus recommended over this one.

Parameters

poly	The polynomial to use omitting the leading x^16 coefficient
seed	Initial value for the CRC computation
src	Input bytes for the computation
len	Length of the input in bytes

Returns

The computed CRC16 value (without any XOR applied to it)

crc16_ansi()

static uint16_t crc16_ansi ( const uint8_t *  src, size_t  len  )

inlinestatic

#include <zephyr/sys/crc.h>

Compute the ANSI (or Modbus) variant of CRC-16.

The ANSI variant of CRC-16 uses 0x8005 (0xA001 reflected) as its polynomial with the initial * value set to 0xffff.

Parameters

src	Input bytes for the computation
len	Length of the input in bytes

Returns

The computed CRC16 value

crc16_ccitt()

uint16_t crc16_ccitt	(	uint16_t	seed,
		const uint8_t *	src,
		size_t	len
	)

#include <zephyr/sys/crc.h>

Compute the checksum of a buffer with polynomial 0x1021, reflecting input and output.

This function is able to calculate any CRC that uses 0x1021 as it polynomial and requires reflecting both the input and the output. It is a fast variant that runs in O(n) time, where n is the length of the input buffer.

The following checksums can, among others, be calculated by this function, depending on the value provided for the initial seed and the value the final calculated CRC is XORed with:

• CRC-16/CCITT, CRC-16/CCITT-TRUE, CRC-16/KERMIT https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-kermit initial seed: 0x0000, xor output: 0x0000
• CRC-16/X-25, CRC-16/IBM-SDLC, CRC-16/ISO-HDLC https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-ibm-sdlc initial seed: 0xffff, xor output: 0xffff

Note

To calculate the CRC across non-contiguous blocks use the return value from block N-1 as the seed for block N.

See ITU-T Recommendation V.41 (November 1988).

Parameters

seed	Value to seed the CRC with
src	Input bytes for the computation
len	Length of the input in bytes

Returns

The computed CRC16 value (without any XOR applied to it)

crc16_itu_t()

uint16_t crc16_itu_t	(	uint16_t	seed,
		const uint8_t *	src,
		size_t	len
	)

#include <zephyr/sys/crc.h>

Compute the checksum of a buffer with polynomial 0x1021, no reflection of input or output.

This function is able to calculate any CRC that uses 0x1021 as it polynomial and requires no reflection on both the input and the output. It is a fast variant that runs in O(n) time, where n is the length of the input buffer.

The following checksums can, among others, be calculated by this function, depending on the value provided for the initial seed and the value the final calculated CRC is XORed with:

• CRC-16/XMODEM, CRC-16/ACORN, CRC-16/LTE https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-xmodem initial seed: 0x0000, xor output: 0x0000
• CRC16/CCITT-FALSE, CRC-16/IBM-3740, CRC-16/AUTOSAR https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-ibm-3740 initial seed: 0xffff, xor output: 0x0000
• CRC-16/GSM https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-gsm initial seed: 0x0000, xor output: 0xffff

Note

To calculate the CRC across non-contiguous blocks use the return value from block N-1 as the seed for block N.

See ITU-T Recommendation V.41 (November 1988) (MSB first).

Parameters

seed	Value to seed the CRC with
src	Input bytes for the computation
len	Length of the input in bytes

Returns

The computed CRC16 value (without any XOR applied to it)

crc16_reflect()

uint16_t crc16_reflect	(	uint16_t	poly,
		uint16_t	seed,
		const uint8_t *	src,
		size_t	len
	)

#include <zephyr/sys/crc.h>

Generic function for computing a CRC-16 with input and output reflection.

Compute CRC-16 by passing in the address of the input, the input length and polynomial used in addition to the initial value. This is O(n*8) where n is the length of the buffer provided. Both input and output are reflected.

Note

If you are planning to use a CRC based on poly 0x1012 the function crc16_ccitt() is faster and thus recommended over this one.

The following checksums can, among others, be calculated by this function, depending on the value provided for the initial seed and the value the final calculated CRC is XORed with:

• CRC-16/ANSI, CRC-16/MODBUS, CRC-16/USB, CRC-16/IBM https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-modbus poly: 0x8005 (0xA001) initial seed: 0xffff, xor output: 0x0000

Parameters

poly	The polynomial to use omitting the leading x^16 coefficient. Important: please reflect the poly. For example, use 0xA001 instead of 0x8005 for CRC-16-MODBUS.
seed	Initial value for the CRC computation
src	Input bytes for the computation
len	Length of the input in bytes

Returns

The computed CRC16 value (without any XOR applied to it)

crc32_c()

uint32_t crc32_c	(	uint32_t	crc,
		const uint8_t *	data,
		size_t	len,
		bool	first_pkt,
		bool	last_pkt
	)

#include <zephyr/sys/crc.h>

Calculate CRC32C (Castagnoli) checksum.

Parameters

crc	CRC32C checksum that needs to be updated.
data	Pointer to data on which the CRC should be calculated.
len	Data length.
first_pkt	Whether this is the first packet in the stream.
last_pkt	Whether this is the last packet in the stream.

Returns

CRC32 value.

crc32_ieee()

uint32_t crc32_ieee	(	const uint8_t *	data,
		size_t	len
	)

#include <zephyr/sys/crc.h>

Generate IEEE conform CRC32 checksum.

Parameters

data	Pointer to data on which the CRC should be calculated.
len	Data length.

Returns

CRC32 value.

crc32_ieee_update()

uint32_t crc32_ieee_update	(	uint32_t	crc,
		const uint8_t *	data,
		size_t	len
	)

#include <zephyr/sys/crc.h>

Update an IEEE conforming CRC32 checksum.

Parameters

crc	CRC32 checksum that needs to be updated.
data	Pointer to data on which the CRC should be calculated.
len	Data length.

Returns

CRC32 value.

crc4()

uint8_t crc4	(	const uint8_t *	src,
		size_t	len,
		uint8_t	polynomial,
		uint8_t	initial_value,
		bool	reversed
	)

#include <zephyr/sys/crc.h>

Generic function for computing CRC 4.

Compute CRC 4 by passing in the address of the input, the input length and polynomial used in addition to the initial value. The input buffer must be aligned to a whole byte. It is guaranteed that 4 most significant bits of the result will be set to zero.

Parameters

src	Input bytes for the computation
len	Length of the input in bytes
polynomial	The polynomial to use omitting the leading x^4 coefficient
initial_value	Initial value for the CRC computation
reversed	Should we use reflected/reversed values or not

Returns

The computed CRC4 value

crc4_ti()

uint8_t crc4_ti	(	uint8_t	seed,
		const uint8_t *	src,
		size_t	len
	)

#include <zephyr/sys/crc.h>

Compute the CRC-4 checksum of a buffer.

Used by the TMAG5170 sensor. Uses 0x03 as the polynomial with no reflection. 4 most significant bits of the CRC result will be set to zero.

Parameters

seed	Value to seed the CRC with
src	Input bytes for the computation
len	Length of the input in bytes

Returns

The computed CRC4 value

crc7_be()

uint8_t crc7_be	(	uint8_t	seed,
		const uint8_t *	src,
		size_t	len
	)

#include <zephyr/sys/crc.h>

Compute the CRC-7 checksum of a buffer.

See JESD84-A441. Used by the MMC protocol. Uses 0x09 as the polynomial with no reflection. The CRC is left justified, so bit 7 of the result is bit 6 of the CRC.

Parameters

seed	Value to seed the CRC with
src	Input bytes for the computation
len	Length of the input in bytes

Returns

The computed CRC7 value

crc8()

uint8_t crc8	(	const uint8_t *	src,
		size_t	len,
		uint8_t	polynomial,
		uint8_t	initial_value,
		bool	reversed
	)

#include <zephyr/sys/crc.h>

Generic function for computing CRC 8.

Compute CRC 8 by passing in the address of the input, the input length and polynomial used in addition to the initial value.

Parameters

src	Input bytes for the computation
len	Length of the input in bytes
polynomial	The polynomial to use omitting the leading x^8 coefficient
initial_value	Initial value for the CRC computation
reversed	Should we use reflected/reversed values or not

Returns

The computed CRC8 value

crc8_ccitt()

uint8_t crc8_ccitt	(	uint8_t	initial_value,
		const void *	buf,
		size_t	len
	)

#include <zephyr/sys/crc.h>

Compute CCITT variant of CRC 8.

Normal CCITT variant of CRC 8 is using 0x07.

Parameters

initial_value	Initial value for the CRC computation
buf	Input bytes for the computation
len	Length of the input in bytes

Returns

The computed CRC8 value

crc_by_type()

static uint32_t crc_by_type ( enum crc_type  type, const uint8_t *  src, size_t  len, uint32_t  seed, uint32_t  poly, bool  reflect, bool  first, bool  last  )

inlinestatic

#include <zephyr/sys/crc.h>

Compute a CRC checksum, in a generic way.

This is a dispatch function that calls the individual CRC routine determined by type.

For 7, 8, and 16-bit CRCs, the relevant seed and poly values should be passed in via the least-significant byte(s).

Similarly, for 7, 8, and 16-bit CRCs, the relevant result is stored in the least-significant byte(s) of the returned value.

Parameters

type	CRC algorithm to use.
src	Input bytes for the computation
len	Length of the input in bytes
seed	Value to seed the CRC with
poly	The polynomial to use omitting the leading coefficient
reflect	Should we use reflected/reversed values or not
first	Whether this is the first packet in the stream.
last	Whether this is the last packet in the stream.

Returns

uint32_t the computed CRC value