SS-68BB USB USER MANUAL
DOC. NO: SS-68BB USB-14 (REV 04)
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The process has been automated and the code can be set and tested using the 'Buffer
Lock' tool.
Challenging the buffer
The command to challenge the buffer is: 'CODErrr..rrr<enter>' where 'CODE' is the
command, 'rrr..rrr' is the random challenge string up to 10 characters in length and
<enter> is the Carriage Return character 0x0D.
Buffer response
The buffer will respond with the following:
CODE: hhhh<enter>
Where 'CODE: ' is the response text and 'hhhh' is a 16 bit CRC for the submitted
challenge and the secret key.
Response validation
In the code below the variable CRC is a 16 bit unsigned integer and char is 8 bit. CmdBuf
is the input buffer where the string starting with 'CODE: ' is stored and CmdPtr indexes the
1st 'h'.
void CalcCrc(unsigned char ser_data)
{
crc = (unsigned char)(crc >> 8) | (crc << 8);
crc ^= ser_data;
crc ^= (unsigned char)(crc & 0xff) >> 4;
crc ^= (crc << 8) << 4;
crc ^= ((crc & 0xff) << 4) << 1;
crc &= 0xFFFF;
}
void mfCode(void)
{
char * p = &CmdBuf[CmdPtr];
int retCrc = HexToInt(p,4);
//convert the hex data to int
crc = 0xFFFF;
//initialise the crc
//======== do the calculation on the challenge =============
for (unsigned int i = 0; i < strlen(test); i++)
{
CalcCrc(test[i]);
}
//======== do the calculation on the UserKey =============
for (int i = 0; i < strlen(SecretKey); i++)
{
CalcCrc(SecretKry[i]);
}
//==== crc should be equal to retCrc if all is well ==========
}
