Arduino Serial read and parse HEX

Question

I'm trying to create an Arduino interface for the DMX software Freestyler, but struggling to parse the data received due to knowing the encoding of the data received.

The image bellow is a serial monitor I've attached to Freestyler to see the incoming data, the format is very simple 3 bytes per channel. 1st byte is the startOfMessage, 2nd byte is the channel number, 3rd byte is the channel value.

The serial monitor displays as hexadecimal and decimal.

For testing, I'm trying to switch on an led when the startOfmessage (which is a constant) is correctly parsed.

byte myByte; 
void setup(void){
Serial.begin(9600); // begin serial communication
pinMode(13,OUTPUT);
}

void loop(void) {
if (Serial.available()>0) { // there are bytes in the serial buffer to     read
  while(Serial.available()>0) { // every time a byte is read it is   expunged 
  // from the serial buffer so keep reading the buffer until all the bytes 
  // have been read.
     myByte = Serial.read(); // read in the next byte

  }
  if(myByte == 72){
    digitalWrite(13,HIGH);
  }
  if(myByte == 48){
    digitalWrite(13,HIGH);
  }
  delay(100); // a short delay
  }

 }

Could anyone set me in the right direction?

Answer 1

You must detect startOfMesage and with it, read channel and value. So, read byte from serial until you detect '0x48'

byte myByte, channel, value;
bool lstart = false; //Flag for start of message
bool lchannel = false; //Flag for channel detected
void setup(){
    Serial.begin(9600); // begin serial communication
    pinMode(13,OUTPUT);
}

void loop() {
   if (Serial.available()>0) { // there are bytes in the serial buffer to read
      myByte = Serial.read(); // read in the next byte
      if(myByte == 0x48 && !lstart && !lchannel){ //startOfMessage
         lstart = true;
         digitalWrite(13,HIGH);
      } else {
         if(lstart && !lchannel){ //waiting channel
             lstart = false;
             lchannel = true;
             channel = myByte;
         } else {
            if(!lstart && lchannel){ //waiting value
               lchannel = false;
               value = myByte;
            } else {
               //incorrectByte waiting for startOfMesagge or another problem
            }
         }
      }
   }
}

Not very elegant but could work.