PNI CompassPoint Prime - Manual (Page 62)

PNI Sensor Corporation DOC# 1014177 r08
Prime User Manual – July 2011 Page 56
}
return crc;
}
//
// This is called each time this process gets a turn to execute.
//
void CommProtocol::Control()
{
// InLen returns the number of bytes in the input buffer of
// the serial object that are available for us to read.
UInt32 inLen = mSerialPort->InLen();
switch(mStep)
{
case 1:
{
// wait for length bytes to be received by the
// serial object
if(inLen >= 2)
{
// Read block will return the number of
// requested (or available) bytes that are in
// the serial objects input buffer.
// read the byte count
mSerialPort->ReadBlock(mInData, 2);
// byte count is ALWAYS transmitted in big
// Endian, copy byte count to mExpectedLen to
// native Endianess
mExpectedLen =
(mInData[0] << 8) | mInData[1];
// Ticks is a timer function. 1 tick =
// 10msec.
// wait up to 1/2s for the complete frame
// (mExpectedLen) to be received
mTime = Ticks() + 50 ;
mStep++ ; //go to next step in the process
}
break ;
}
case 2:
{
// wait for msg complete or timeout
if(inLen >= mExpectedLen - 2)
{
// calculated and received crcs.
UInt16 crc, crcReceived;
// Read block will return the number of
// requested (or available) bytes that are in
// the serial objects input buffer.