• C

Logarithm for CRC16


Could anyone give me the logarithm for CRC16 (16 bit CRC)
an example on a short message (about 5 bytes) would be very nice!

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The logarithm?
Probably the algorithm :)
Nice anagram though :)
This is programm for make CRC16 (for messages)
unsigned short CRC(unsigned char *lpuchMsg, unsigned short ushDataLen)
  unsigned char uchCRCHI = 0xFF;
  unsigned char uchCRCLO = 0xFF;
  unsigned uIndex;
  static unsigned char auchCRCHi[] =
   { //1   2     3     4     5    6    7    8    9    10   11  12   13    14   15
     0x00,0xC1, 0x81, 0x40, 0x01,0xc0,0x80,0x41,0x01,0xc0,0x80,0x41,0x00,0xc1,0x81,
     0x40,0x01, 0xc0, 0x80, 0x41,0x00,0xc1,0x81,0x40,0x00,0xc1,0x81,0x40,0x01,0xc0,
     0x80,0x41, 0x01, 0xc0, 0x80,0x41,0x00,0xc1,0x81,0x40,0x00,0xc1,0x81,0x40,0x01,
     0xc0,0x80, 0x41, 0x00, 0xc1,0x81,0x40,0x01,0xc0,0x80,0x41,0x01,0xc0,0x80,0x41,
     0x00,0xC1, 0x81, 0x40, 0x01,0xc0,0x80,0x41,0x00,0xc1,0x81,0x40,0x00,0xc1,0x81,
     0x40,0x01, 0xc0, 0x80, 0x41,0x00,0xc1,0x81,0x40,0x01,0xc0,0x80,0x41,0x01,0xc0,
     0x80,0x41, 0x00, 0xc1, 0x81,0x40,0x00,0xc1,0x81,0x40,0x01,0xc0,0x80,0x41,0x01,
     0xc0,0x80, 0x41, 0x00, 0xc1,0x81,0x40,0x01,0xc0,0x80,0x41,0x00,0xc1,0x81,0x40,
     0x00,0xC1, 0x81, 0x40, 0x01,0xc0,0x80,0x41,0x01,0xc0,0x80,0x41,0x00,0xc1,0x81,
     0x40,0x00, 0xc1, 0x81, 0x40,0x01,0xc0,0x80,0x41,0x00,0xc1,0x81,0x40,0x01,0xc0,
     0x80,0x41, 0x01, 0xc0, 0x80,0x41,0x00,0xc1,0x81,0x40,0x00,0xc1,0x81,0x40,0x01,
     0xC0,0x80, 0x41, 0x01, 0xc0,0x80,0x41,0x00,0xc1,0x81,0x40,0x01,0xc0,0x80,0x41,
     0x00,0xC1, 0x81, 0x40, 0x00,0xc1,0x81,0x40,0x01,0xc0,0x80,0x41,0x00,0xc1,0x81,
     0x40,0x01, 0xc0, 0x80, 0x41,0x01,0xc0,0x80,0x41,0x00,0xc1,0x81,0x40,0x01,0xc0,
     0x80,0x41, 0x00, 0xc1, 0x81,0x40,0x00,0xc1,0x81,0x40,0x01,0xc0,0x80,0x41,0x01,
     0xc0,0x80, 0x41, 0x00, 0xc1,0x81,0x40,0x00,0xc1,0x81,0x40,0x01,0xc0,0x80,0x41,
     0x00,0xC1, 0x81, 0x40, 0x01,0xc0,0x80,0x41,0x01,0xc0,0x80,0x41,0x00,0xc1,0x81,

  static unsigned char auchCRCLo[] =
   { //1   2     3     4     5    6    7    8    9    10   11  12   13    14   15
     0x00,0xC0, 0xc1, 0x01, 0xc3,0x03,0x02,0xc2,0xc6,0x06,0x07,0xc7,0x05,0xc5,0xc4,
     0x04,0xcc, 0x0c, 0x0d, 0xcd,0x0f,0xcf,0xce,0x0e,0x0a,0xca,0xcb,0x0b,0xc9,0x09,
     0x08,0xc8, 0xd8, 0x18, 0x19,0xd9,0x1b,0xdb,0xda,0x1a,0x1e,0xde,0xdf,0x1f,0xdd,
     0x1d,0x1c, 0xdc, 0x14, 0xd4,0xd5,0x15,0xd7,0x17,0x16,0xd6,0xd2,0x12,0x13,0xd3,
     0x11,0xd1, 0xd0, 0x10, 0xf0,0x30,0x31,0xf1,0x33,0xf3,0xf2,0x32,0x36,0xf6,0xf7,
     0x37,0xf5, 0x35, 0x34, 0xf4,0x3c,0xfc,0xfd,0x3d,0xff,0x3f,0x3e,0xfe,0xfa,0x3a,
     0x3b,0x41, 0x39, 0xf9, 0xf8,0x38,0x28,0xe8,0xe9,0x29,0xeb,0x2b,0x2a,0xea,0xee,
     0x2e,0xfb, 0xef, 0x2d, 0xed,0xec,0x2c,0xe4,0x24,0x25,0xe5,0x27,0xe7,0xe6,0x26,
     0x22,0x2f, 0xe3, 0x23, 0xe1,0x21,0x20,0xe0,0xa0,0x60,0x61,0xa1,0x63,0xa3,0xa2,
     0x62,0xe2, 0xa6, 0xa7, 0x67,0xa5,0x65,0x64,0xa4,0x6c,0xac,0xad,0x6d,0xaf,0x6f,
     0x6e,0xae, 0xaa, 0x6a, 0x6b,0xab,0x69,0xa9,0xa8,0x68,0x78,0xb8,0xb9,0x79,0xbb,
     0x7b,0x7a, 0xba, 0xbe, 0x7e,0x7f,0xbf,0x7d,0xbd,0xbc,0x7c,0xb4,0x74,0x75,0xb5,
     0x77,0xb7, 0xb6, 0x76, 0x72,0xb2,0xb3,0x73,0xb1,0x71,0x70,0xb0,0x50,0x90,0x91,
     0x51,0x93, 0x53, 0x52, 0x92,0x96,0x56,0x57,0x97,0x55,0x95,0x94,0x54,0x9c,0x5c,
     0x5d,0x9d, 0x5f, 0x9f, 0x9e,0x5e,0x5a,0x9a,0x9b,0x5b,0x99,0x59,0x5b,0x98,0x88,
     0x4b,0x49, 0x89, 0x4b, 0x8b,0x8a,0x4a,0x4e,0x8e,0x8f,0x4f,0x8d,0x40,0x41,0x8c,
     0x44,0x84, 0x85, 0x45, 0x87,0x47,0x46,0x86,0x82,0x42,0x43,0x83,0x41,0x81,0x80,
      uIndex = uchCRCHI ^ *lpuchMsg++;
      uchCRCHI = uchCRCLO ^ auchCRCHi[uIndex];
      uchCRCLO = auchCRCLo[uIndex];
  return (uchCRCHI<< 8) | uchCRCLO;
Good Luck, Alex

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uffe78Author Commented:
Thanks BSoethers, one point for you...
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