readSerial.h

bool startCharFound = false;
int incomingByte = 0;

String message;

void readSerial(){
  if (Serial.available() > 0) {
      incomingByte = Serial.read();

      char receivedCharacter = (char) incomingByte;

      if(receivedCharacter == '%'){
        startCharFound = false;
      }

      if(startCharFound == true){
        message += receivedCharacter;
      }

      if(receivedCharacter == '#'){
        startCharFound = true;
        message = "";
      }
  }
}