bool transportInit() {
// Reset the state machine
_dev.begin(MY_RS485_BAUD_RATE);
_serialReset();
#if defined(MY_RS485_DE_PIN)
pinMode(MY_RS485_DE_PIN, OUTPUT);
digitalWrite(MY_RS485_DE_PIN, LOW);
#endif
return true;
}
// This is the main reception state machine. Progress through the states
// is keyed on either special control characters, or counted number of bytes
// received. If all the data is in the right format, and the calculated
// checksum matches the received checksum, AND the destination station is
// our station ID, then look for a registered command that matches the
// command code. If all the above is true, execute the command's
// function.
bool _serialProcess()
{
char inch;
unsigned char i;
if (!_dev.available()) {
return false;
}
while(_dev.available()) {
inch = _dev.read();
switch(_recPhase) {
// Case 0 looks for the header. Bytes arrive in the serial interface and get
// shifted through a header buffer. When the start and end characters in
// the buffer match the SOH/STX pair, and the destination station ID matches
// our ID, save the header information and progress to the next state.
case 0:
memcpy(&_header[0],&_header[1],5);
_header[5] = inch;
if ((_header[0] == SOH) && (_header[5] == STX) && (_header[1] != _header[2])) {
_recCalcCS = 0;
_recStation = _header[1];
_recSender = _header[2];
_recCommand = _header[3];
_recLen = _header[4];
for (i=1; i<=4; i++) {
_recCalcCS += _header[i];
}
_recPhase = 1;
_recPos = 0;
//Check if we should process this message
//We reject the message if we are the sender
//We reject if we are not the receiver and message is not a broadcast
if ((_recSender == _nodeId) ||
(_recStation != _nodeId &&
_recStation != BROADCAST_ADDRESS)) {
_serialReset();
break;
}
if (_recLen == 0) {
_recPhase = 2;
}
}
break;
// Case 1 receives the data portion of the packet. Read in "_recLen" number
// of bytes and store them in the _data array.
case 1:
_data[_recPos++] = inch;
_recCalcCS += inch;
if (_recPos == _recLen) {
_recPhase = 2;
}
break;
// After the data comes a single ETX character. Do we have it? If not,
// reset the state machine to default and start looking for a new header.
case 2:
// Packet properly terminated?
if (inch == ETX) {
_recPhase = 3;
} else {
_serialReset();
}
break;
// Next comes the checksum. We have already calculated it from the incoming
// data, so just store the incoming checksum byte for later.
case 3:
_recCS = inch;
_recPhase = 4;
break;
// The final state - check the last character is EOT and that the checksum matches.
// If that test passes, then look for a valid command callback to execute.
// Execute it if found.
case 4:
if (inch == EOT) {
if (_recCS == _recCalcCS) {
// First, check for system level commands. It is possible
// to register your own callback as well for system level
// commands which will be called after the system default
// hook.
switch (_recCommand) {
case ICSC_SYS_PACK:
_packet_from = _recSender;
_packet_len = _recLen;
_packet_received = true;
break;
}
}
}
//Clear the data
_serialReset();
//Return true, we have processed one command
return true;
break;
}
}
return true;
}
