int incomingByte = 0;

void setup() {
  // put your setup code here, to run once:
  pinMode(07, OUTPUT);//L1
  pinMode(06, OUTPUT);//L2
  pinMode(05, OUTPUT);//R1
  pinMode(04, OUTPUT);//R2
  Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
  Serial.println("Ready...");
}

void stop() {
  digitalWrite(07, LOW);
  digitalWrite(06, LOW);
  digitalWrite(05, LOW);
  digitalWrite(04, LOW);
}

void forward() {
  digitalWrite(07, HIGH);
  digitalWrite(06, LOW);
  digitalWrite(05, HIGH);
  digitalWrite(04, LOW);
}

void backward() {
  digitalWrite(07, LOW);
  digitalWrite(06, HIGH);
  digitalWrite(05, LOW);
  digitalWrite(04, HIGH);
}

void LeftTurn() {
  digitalWrite(07, LOW);
  digitalWrite(06, LOW);
  digitalWrite(05, HIGH);
  digitalWrite(04, LOW);
}

void RightTurn() {
  digitalWrite(07, HIGH);
  digitalWrite(06, LOW);
  digitalWrite(05, LOW);
  digitalWrite(04, LOW);
}

void loop() {
  // reply only when you receive data:
  if (Serial.available()>0) {
    // read the incoming byte:
    incomingByte = Serial.read();

    // say what you got:
    Serial.print("I received: ");
    Serial.println(incomingByte, DEC);
    if (incomingByte==56) {
      forward();
      Serial.println("Forward");
    }
    if (incomingByte==50){
      backward();
      Serial.println("Backward");
    }
    if(incomingByte==53){
      stop();
      Serial.println("Stop");
    }
    if(incomingByte==52){
      LeftTurn();
      Serial.println("Left Turn");
    }
    if(incomingByte==54){
      RightTurn();
      Serial.println("Right Turn");
    }
    }
}