I need a XFP complient CRC code module. Or I need to validate the one that I got. So any help (pointers to code, pointers to XFP CRC spec, notes on how to validate) would help. Sean
One of the things I wanted to have here was a place where anyone who had similar needs could come and be satisified. Between your comments and my code, I believe that this has been done. Keywords: (do they search the contents of the messages?) XFP SMBus PEC packet error correction CRC8 CRC-8. Well those are the ones that I used to try to find this place. I will repost the code with your excelent corrections: /* * Function: Do_CRC8 * * Description: * Computes the CRC value given the byte and the old CRC value as a static value * * Return Value: CRC value * Parameters: Input data byte to be CRC'ed * Remarks: * uses a table driven method to speed things up. * * */ unsigned char Do_CRC8(unsigned char xx) { // this procedure calculates const unsigned char code Table[256]={ 0x00,0x07,0x0E,0x09,0x1C,0x1B,0x12,0x15,0x38,0x3F,0x36,0x31,0x24,0x23,0x2A,0x2D, 0x70,0x77,0x7E,0x79,0x6C,0x6B,0x62,0x65,0x48,0x4F,0x46,0x41,0x54,0x53,0x5A,0x5D, 0xE0,0xE7,0xEE,0xE9,0xFC,0xFB,0xF2,0xF5,0xD8,0xDF,0xD6,0xD1,0xC4,0xC3,0xCA,0xCD, 0x90,0x97,0x9E,0x99,0x8C,0x8B,0x82,0x85,0xA8,0xAF,0xA6,0xA1,0xB4,0xB3,0xBA,0xBD, 0xC7,0xC0,0xC9,0xCE,0xDB,0xDC,0xD5,0xD2,0xFF,0xF8,0xF1,0xF6,0xE3,0xE4,0xED,0xEA, 0xB7,0xB0,0xB9,0xBE,0xAB,0xAC,0xA5,0xA2,0x8F,0x88,0x81,0x86,0x93,0x94,0x9D,0x9A, 0x27,0x20,0x29,0x2E,0x3B,0x3C,0x35,0x32,0x1F,0x18,0x11,0x16,0x03,0x04,0x0D,0x0A, 0x57,0x50,0x59,0x5E,0x4B,0x4C,0x45,0x42,0x6F,0x68,0x61,0x66,0x73,0x74,0x7D,0x7A, 0x89,0x8E,0x87,0x80,0x95,0x92,0x9B,0x9C,0xB1,0xB6,0xBF,0xB8,0xAD,0xAA,0xA3,0xA4, 0xF9,0xFE,0xF7,0xF0,0xE5,0xE2,0xEB,0xEC,0xC1,0xC6,0xCF,0xC8,0xDD,0xDA,0xD3,0xD4, 0x69,0x6E,0x67,0x60,0x75,0x72,0x7B,0x7C,0x51,0x56,0x5F,0x58,0x4D,0x4A,0x43,0x44, 0x19,0x1E,0x17,0x10,0x05,0x02,0x0B,0x0C,0x21,0x26,0x2F,0x28,0x3D,0x3A,0x33,0x34, 0x4E,0x49,0x40,0x47,0x52,0x55,0x5C,0x5B,0x76,0x71,0x78,0x7F,0x6A,0x6D,0x64,0x63, 0x3E,0x39,0x30,0x37,0x22,0x25,0x2C,0x2B,0x06,0x01,0x08,0x0F,0x1A,0x1D,0x14,0x13, 0xAE,0xA9,0xA0,0xA7,0xB2,0xB5,0xBC,0xBB,0x96,0x91,0x98,0x9F,0x8A,0x8D,0x84,0x83, 0xDE,0xD9,0xD0,0xD7,0xC2,0xC5,0xCC,0xCB,0xE6,0xE1,0xE8,0xEF,0xFA,0xFD,0xF4,0xF3 }; ucCRC=Table[ucCRC ^ xx]; return (ucCRC); }
"...come and be satisified. OK Sean. Good job. To your contribution, I'll add another that uses a nibble-oriented feedback table for situations where one is tight on code space (for the table) and can give up a little performance.
/**************************************************************************** * * NAME: Crc8() * PURPOSE: Generate 8-bit CRC. * * SYNOPSIS: unsigned char Crc8(unsigned char b, unsigned char initCrc); * * INTERFACE PARAMETERS: * * Name FG-IO Description * ------------------- ----- ----------------------------------------- * b F I Data byte to CRC (MSBit first). * initCrc F I Initial CRC or CRC accumulator for * continuation. * <return value> O CRC. * * DESCRIPTION: * * The function returns the 8-bit CRC after including "b" with the * initial CRC "initCRC". * ****************************************************************************/ unsigned char Crc8(unsigned char b, unsigned char initCrc) { static const unsigned char code feedback[16] = { 0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15, 0x38, 0x3F, 0x36, 0x31, 0x24, 0x23, 0x2A, 0x2D }; #define CRC initCrc CRC = (CRC << 4) ^ feedback[((CRC ) ^ b) >> 4]; CRC = (CRC << 4) ^ feedback[((CRC >> 4) ^ b) & 0x0F]; return (CRC); #undef CRC }