char C;
void setup() 
{
  Serial.begin(115200);
  pinMode(13,OUTPUT);
}

void loop() 
{
  int n = Serial.available();
  if(n>0)
  {
     C = Serial.read();
     if(C == '0')
     {
        digitalWrite(13,0);  // LED Off
     }
     if(C == '1')
     {
        digitalWrite(13,1);  // LED On
     }
  }

  if(C == '2')
  {
     digitalWrite(13,1);
     delay(200);
     digitalWrite(13,0);
     delay(200);
  }
  if(C == '3')
  {
     digitalWrite(13,1);
     delay(3);
     digitalWrite(13,0);
     delay(20);
  }
}