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/****************************************************************************
*
* Copyright (c) 2006 Dave Hylands <dhylands@gmail.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Alternatively, this software may be distributed under the terms of BSD
* license.
*
* See README and COPYING for more details.
*
****************************************************************************/
/**
*
* @file Crc8.c
*
* @brief This file contains the definition of the CRC-8 algorithim
* used by SMBus
*
*
*****************************************************************************/
/* ---- Include Files ----------------------------------------------------- */
#include "Config.h"
#include "Crc8.h"
#include "Log.h"
/* ---- Public Variables -------------------------------------------------- */
/* ---- Private Constants and Types --------------------------------------- */
/* ---- Private Variables ------------------------------------------------- */
/* ---- Private Function Prototypes --------------------------------------- */
/* ---- Functions --------------------------------------------------------- */
/****************************************************************************/
/**
* Calculates the CRC-8 used as part of SMBus.
*
* CRC-8 is defined to be x^8 + x^2 + x + 1
*
* To use this function use the following template:
*
* crc = Crc8( crc, data );
*/
#if 0 // Traditional implementation
#define POLYNOMIAL (0x1070U << 3)
unsigned char Crc8( unsigned char inCrc, unsigned char inData )
{
int i;
unsigned short data;
data = inCrc ^ inData;
data <<= 8;
for ( i = 0; i < 8; i++ )
{
if (( data & 0x8000 ) != 0 )
{
data = data ^ POLYNOMIAL;
}
data = data << 1;
}
#if 0
#if defined( LogBuf2 )
LogBuf2( "Crc8: data:0x%02x crc:0x%02x\n", inData, (unsigned char)( data >> 8 ));
#else
Log( "Crc8: data:0x%02x crc:0x%02x\n", inData, (unsigned char)( data >> 8 ));
#endif
#endif
return (unsigned char)( data >> 8 );
} // Crc8
#else // Optimized for 8 bit CPUs (0x22 bytes on ATMega128 versus 0x30 for above version)
unsigned char Crc8( unsigned char inCrc, unsigned char inData )
{
unsigned char i;
unsigned char data;
data = inCrc ^ inData;
for ( i = 0; i < 8; i++ )
{
if (( data & 0x80 ) != 0 )
{
data <<= 1;
data ^= 0x07;
}
else
{
data <<= 1;
}
}
#if 0
#if defined( LogBuf2 )
LogBuf2( "Crc8: data:0x%02x crc:0x%02x\n", inData, data );
#else
Log( "Crc8: data:0x%02x crc:0x%02x\n", inData, data );
#endif
#endif
return data;
} // Crc8
#endif
#if defined( CFG_CRC8BLOCK )
/****************************************************************************/
/**
* Calculates the CRC-8 used as part of SMBus over a block of memory.
*/
uint8_t Crc8Block( uint8_t crc, uint8_t *data, uint8_t len )
{
while ( len > 0 )
{
crc = Crc8( crc, *data++ );
len--;
}
return crc;
} // Crc8Block
#endif // CFG_CRC8BLOCK
/** @} */
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