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CRC Algorithm

The algorithm used to create the CRC follows:

const unsigned short crcTable[256] = {

0x0000, 0x0108, 0x0210, 0x0318, 0x0420, 0x0528, 0x0630, 0x0738,

0x0840, 0x0948, 0x0A50, 0x0B58, 0x0C60, 0x0D68, 0x0E70, 0x0F78,

0x1081, 0x1189, 0x1291, 0x1399, 0x14A1, 0x15A9, 0x16B1, 0x17B9,

0x18C1, 0x19C9, 0x1AD1, 0x1BD9, 0x1CE1, 0x1DE9, 0x1EF1, 0x1FF9,

0x2102, 0x200A, 0x2312, 0x221A, 0x2522, 0x242A, 0x2732, 0x263A,

0x2942, 0x284A, 0x2B52, 0x2A5A, 0x2D62, 0x2C6A, 0x2F72, 0x2E7A,

0x3183, 0x308B, 0x3393, 0x329B, 0x35A3, 0x34AB, 0x37B3, 0x36BB,

0x39C3, 0x38CB, 0x3BD3, 0x3ADB, 0x3DE3, 0x3CEB, 0x3FF3, 0x3EFB,

0x4204, 0x430C, 0x4014, 0x411C, 0x4624, 0x472C, 0x4434, 0x453C,

0x4A44, 0x4B4C, 0x4854, 0x495C, 0x4E64, 0x4F6C, 0x4C74, 0x4D7C,

0x5285, 0x538D, 0x5095, 0x519D, 0x56A5, 0x57AD, 0x54B5, 0x55BD,

0x5AC5, 0x5BCD, 0x58D5, 0x59DD, 0x5EE5, 0x5FED, 0x5CF5, 0x5DFD,

0x6306, 0x620E, 0x6116, 0x601E, 0x6726, 0x662E, 0x6536, 0x643E,

0x6B46, 0x6A4E, 0x6956, 0x685E, 0x6F66, 0x6E6E, 0x6D76, 0x6C7E,

0x7387, 0x728F, 0x7197, 0x709F, 0x77A7, 0x76AF, 0x75B7, 0x74BF,

0x7BC7, 0x7ACF, 0x79D7, 0x78DF, 0x7FE7, 0x7EEF, 0x7DF7, 0x7CFF,

0x8408, 0x8500, 0x8618, 0x8710, 0x8028, 0x8120, 0x8238, 0x8330,

0x8C48, 0x8D40, 0x8E58, 0x8F50, 0x8868, 0x8960, 0x8A78, 0x8B70,

0x9489, 0x9581, 0x9699, 0x9791, 0x90A9, 0x91A1, 0x92B9, 0x93B1,

0x9CC9, 0x9DC1, 0x9ED9, 0x9FD1, 0x98E9, 0x99E1, 0x9AF9, 0x9BF1,

0xA50A, 0xA402, 0xA71A, 0xA612, 0xA12A, 0xA022, 0xA33A, 0xA232,

0xAD4A, 0xAC42, 0xAF5A, 0xAE52, 0xA96A, 0xA862, 0xAB7A, 0xAA72,

0xB58B, 0xB483, 0xB79B, 0xB693, 0xB1AB, 0xB0A3, 0xB3BB, 0xB2B3,

0xBDCB, 0xBCC3, 0xBFDB, 0xBED3, 0xB9EB, 0xB8E3, 0xBBFB, 0xBAF3,

0xC60C, 0xC704, 0xC41C, 0xC514, 0xC22C, 0xC324, 0xC03C, 0xC134,

0xCE4C, 0xCF44, 0xCC5C, 0xCD54, 0xCA6C, 0xCB64, 0xC87C, 0xC974,

0xD68D, 0xD785, 0xD49D, 0xD595, 0xD2AD, 0xD3A5, 0xD0BD, 0xD1B5,

0xDECD, 0xDFC5, 0xDCDD, 0xDDD5, 0xDAED, 0xDBE5, 0xD8FD, 0xD9F5,

0xE70E, 0xE606, 0xE51E, 0xE416, 0xE32E, 0xE226, 0xE13E, 0xE036,

0xEF4E, 0xEE46, 0xED5E, 0xEC56, 0xEB6E, 0xEA66, 0xE97E, 0xE876,

0xF78F, 0xF687, 0xF59F, 0xF497, 0xF3AF, 0xF2A7, 0xF1BF, 0xF0B7,

0xFFCF, 0xFEC7, 0xFDDF, 0xFCD7, 0xFBEF, 0xFAE7, 0xF9FF, 0xF8F7,

};

unsigned short Crc (unsigned short lastCrc, unsigned long sizeOfBuffer,

unsigned char *buffer) {

unsigned long i;

unsigned char index;

for (i = 0L; i < sizeOfBuffer; i++) {

index = buffer[i] ^ ((unsigned char)(lastCrc & 0x00FF));

lastCrc = ((lastCrc >> 8) & 0x00FF) ^ (crcTable[index]);

}

return (lastCrc);

}



CRC Test Program

The following program can be used to test the above:

#include <stdio.h>

int main(void) {

unsigned char buffer [] = {0, 0, 0, 0, 0, 0x77, 0xCF};

printf(“CRC(Expected 0x73F3) = 0x%04X\n”, Crc(0x0, 7, buffer));

return(0);

}

NOTE: For the example above, the value for the last CRC

parameter should be initalized to zero (0).

Try using HB_CRC32().

EMG

Jeff,

FWH provides:

nFileCRC( cFileName ) --> nCRC

nStrCRC( cString ) --> nCRC

Enrico/Antonio,

The problem is that the CRC can only be a 4 char hex string.

Here is an example of the error codes returned with their correct CRC values:

DIAP000<%REQUEST CORRUPT>734D

DIAP000<%INVALID CRC CHAR>A471

I am just so lost on this one. I have send an email to the manufacturer of the device but I have no idea when they will reply and I need to provide an answer to end user today.

Any help you can provide will be greatly appreciated.

Jeff,

You can use FWH DecToHex():

DecToHex( nFileCRC( cFileName ) )

DecToHex( nStrCRC( cString ) )

Jeff,

A hex number of four characters can hold a number <= 65535

So if the number is larger than 65535 (FFFF) then you can not use four characters only.

I have written a small app that will send the command with 0000 to FFFF and see what CRC works. It is going to take a while but I can not figure out how they generate this 4 char hex either.

Thanks for the effort ... You know they will finally get back to me after it has been figured out

Maybe you'd need of a CRC16 function.

EMG

Is there a CRC16 function?

The fixed value of 128 has to be calculated using strlen() instead.

EMG