Appendix B Communication Protocol Shenzhen Hpmont Technology Co., Ltd
―140― HD5L Series Controller User Manual
9. CRC checking
In order to satisfy speed increase needs, CRC-16 normally adopts form mode. The following is
CRC-16 C language channel code. Please note the final result has exchanged the higher and
lower bytes. That is the right CRC checksum to be sent.
unsigned short CRC16 ( unsigned char *msg, unsigned char length)
/* The function returns the CRC as a unsigned short type */
{
/* high byte of CRC initialized */
unsigned char uchCRCHi = 0xFF ;
/* low byte of CRC initialized */
unsigned char uchCRCLo = 0xFF ;
/* index into CRC look up table */
unsigned uIndex ;
/* pass through message buffer */
While (length--)
{
/* calculate the CRC */
uIndex = uchCRCLo ^ *msg++ ;
uchCRCLo = uchCRCHi ^ (crcvalue[uIndex] >>8);
uchCRCHi =crcvalue[uIndex]&0xff;
}
return (uchCRCHi | uchCRCLo<<8) ;
}
/* Table of CRC values */
const unsigned int crcvalue[ ] = {
0x0000,0xC1C0,0x81C1,0x4001,0x01C3,0xC003,0x8002,0x41C2,0x01C6,0xC006,0x8007,
0x41C7,0x0005,0xC1C5,0x81C4,0x4004,0x01CC,0xC00C,0x800D,0x41CD,0x000F,0xC1CF,
0x81CE,0x400E,0x000A,0xC1CA,0x81CB,0x400B,0x01C9,0xC009,0x8008,0x41C8,0x01D8,
0xC018,0x8019,0x41D9,0x001B,0xC1DB,0x81DA,0x401A,0x001E,0xC1DE,0x81DF,0x401F,
0x01DD,0xC01D,0x801C,0x41DC,0x0014,0xC1D4,0x81D5,0x4015,0x01D7,0xC017,0x8016,
0x41D6,0x01D2,0xC012,0x8013,0x41D3,0x0011,0xC1D1,0x81D0,0x4010,0x01F0,0xC030,
0x8031,0x41F1,0x0033,0xC1F3,0x81F2,0x4032,0x0036,0xC1F6,0x81F7,0x4037,0x01F5,
0xC035,0x8034,0x41F4,0x003C,0xC1FC,0x81FD,0x403D,0x01FF,0xC03F,0x803E,0x41FE,
0x01FA,0xC03A,0x803B,0x41FB,0x0039,0xC1F9,0x81F8,0x4038,0x0028,0xC1E8,0x81E9,
0x4029,0x01EB,0xC02B,0x802A,0x41EA,0x01EE,0xC02E,0x802F,0x41EF,0x002D,0xC1ED,
0x81EC,0x402C,0x01E4,0xC024,0x8025,0x41E5,0x0027,0xC1E7,0x81E6,0x4026,0x0022,
0xC1E2,0x81E3,0x4023,0x01E1,0xC021,0x8020,0x41E0,0x01A0,0xC060,0x8061,0x41A1,
0x0063,0xC1A3,0x81A2,0x4062,0x0066,0xC1A6,0x81A7,0x4067,0x01A5,0xC065,0x8064,
0x41A4,0x006C,0xC1AC,0x81AD,0x406D,0x01AF,0xC06F,0x806E,0x41AE,0x01AA,0xC06A,
0x806B,0x41AB,0x0069,0xC1A9,0x81A8,0x4068,0x0078,0xC1B8,0x81B9,0x4079,0x01BB,
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