crc.h File Reference

Detailed Description

This implementation follows the "bad CRC16-CCITT" algorithm, as described in http://srecord.sourceforge.net/crc16-ccitt.html.

Definition in file crc.h.

Go to the source code of this file.

Functions
uint16_t	Crc_addByte (uint16_t crc, uint8_t byte)
uint16_t	Crc_fromBuffer (const uint8_t *buf, uint32_t len)
uint16_t	Crc_fromBuffer32 (const uint32_t *buf, uint32_t len)

Data Structures
union	crc_t
struct	crc_t.__unnamed__

Macros
#define	CRC_CCITT_FAST_LUT
#define	Crc_initValue()   0xffff

Function Documentation

Crc_addByte()

uint16_t Crc_addByte	(	uint16_t	crc,
		uint8_t	byte
	)

Add byte to CRC result

Parameters

crc	Cumulative result of CRC calculation
byte	The byte to add to the result

Note

90.1 us for 50 bytes -> 1.80 us per byte for CRC_CCITT_FAST_LUT

96.4 us for 50 bytes -> 1.93 us per byte for CRC_CCITT_LEGACY

Crc_fromBuffer()

uint16_t Crc_fromBuffer	(	const uint8_t *	buf,
		uint32_t	len
	)

Calculate CRC over a buffer

Parameters

buf	Pointer to a buffer
len	Length of the buffer in bytes

Note

63.8 us for 50 bytes -> 1.28 us per byte for CRC_CCITT_FAST_LUT

92.1 us for 50 bytes -> 1.84 us per byte for CRC_CCITT_LEGACY

Crc_fromBuffer32()

uint16_t Crc_fromBuffer32	(	const uint32_t *	buf,
		uint32_t	len
	)

Calculate CRC over a buffer

Parameters

buf	Pointer to a buffer
len	Length of the buffer in words

Note

Approximately 65% execution time compared to uint8_t version when calculating checksums from ROM contents

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Data Structure Documentation

crc_t

union crc_t

Definition at line 27 of file crc.h.

Data Fields
struct crc_t	__unnamed__
uint16_t	crc

crc_t.__unnamed__

struct crc_t.__unnamed__

Definition at line 29 of file crc.h.

Data Fields
uint8_t	lsb
uint8_t	msb

Macro Definition Documentation

CRC_CCITT_FAST_LUT

#define CRC_CCITT_FAST_LUT

Fast LUT based algorithm. Original CRC algorithm, ported 1:1 from PIC18F

Definition at line 22 of file crc.h.

Crc_initValue

#define Crc_initValue

(

)

0xffff

Startup value for CRC result

Definition at line 40 of file crc.h.