PNI TCM 5 - Manual (Page 51)

PNI Sensor Corporation Doc #1007537 r12
TCM3 & TCM5 User Manual – Sept 2012 Page 51
// Store the total len of the packet including the len bytes (2), the frame ID (1),
// the data (len), and the crc (2). If no data is sent, the min len is 5
mOutData[index++] = count >> 8 ;
mOutData[index++] = count & 0xFF ;
// store the frame ID
mOutData[index++] = frameType ;
// copy the data to be sent
while (len--) mOutData[index++] = *data++;
// compute and add the crc
crc = CRC(mOutData, index);
mOutData[index++] = crc >> 8 ;
mOutData[index++] = crc & 0xFF ;
// Write block will copy and send the data out the serial port
mSerialPort->WriteBlock(mOutData, index);
}
//
// Call the functions in serial port necessary to change the baud rate
//
void CommProtocol::SetBaud(UInt32 baud)
{
mSerialPort->SetBaudRate(baud);
mSerialPort->InClear(); // clear any data that was already waiting in the
buffer
}
//
// Update the CRC for transmitted and received data using the CCITT 16bit algorithm (X^16 + X^12
+ X^5 + 1).
//
UInt16 CommProtocol::CRC( void * data, UInt32 len)
{
UInt8 * dataPtr = (UInt8 *)data;
UInt32 index = 0 ;
UInt16 crc = 0 ;
while (len--)
{
crc = ( unsigned char )(crc >> 8 ) | (crc << 8 );
crc ^= dataPtr[index++];
crc ^= ( unsigned char )(crc & 0xff ) >> 4 ;