int led = 13;
int IN1 = 6;
int IN2 = 7;
int IN3 = 8;
int IN4 = 9;
int EN1 = 10;
int EN2 = 11;


char A;
int i = 0;
void setup()
{
  
  Serial.begin(9600);
  pinMode (led, OUTPUT);
  pinMode (IN1, OUTPUT);
  pinMode (IN2, OUTPUT);
  pinMode (IN3, OUTPUT);
  pinMode (IN4, OUTPUT);


  digitalWrite(led, HIGH);
  delay(300);
  digitalWrite(led, LOW);
  delay(300);
  digitalWrite(led, HIGH);
  delay(300);
  digitalWrite(led, LOW);
  delay(500);
  digitalWrite(led, HIGH);
  delay(1000);
  digitalWrite(led, LOW);
  delay(300);
}

void loop()
{
  
  analogWrite (EN1, 150);
  analogWrite (EN2, 150);

 while (Serial.available())
  {    
    Stop(); 
    A = Serial.read();
    switch (A)
    {
      case'F': forward();
        break;
      case'B': backward();
        break;
      case'L': Left();
        break;
      case'R': Right();
        break;
    }
  }

}
void forward()
{
  Serial.println("Forward");
  digitalWrite (IN1, HIGH);
  digitalWrite (IN2, LOW);
  digitalWrite (IN3, LOW);
  digitalWrite (IN4, HIGH);
}

void backward()
{
  Serial.println("Backward");
  digitalWrite (IN1, LOW);
  digitalWrite (IN2, HIGH);
  digitalWrite (IN3, HIGH);
  digitalWrite (IN4, LOW);
}

void Left()
{
  Serial.println("Left");
  digitalWrite (IN1, LOW);
  digitalWrite (IN2, HIGH);
  digitalWrite (IN3, LOW);
  digitalWrite (IN4, HIGH);
}

void Right()
{
  Serial.println("Right");
  digitalWrite (IN1, HIGH);
  digitalWrite (IN2, LOW);
  digitalWrite (IN3, HIGH);
  digitalWrite (IN4, LOW);
}

void Stop()
{
  Serial.println("Stop");
  digitalWrite (IN1, LOW);
  digitalWrite (IN2, LOW);
  digitalWrite (IN3, LOW);
  digitalWrite (IN4, LOW);
}