void setup() 
{
 pinMode (13,OUTPUT);
 Serial.begin(9600);
}
 
void loop() 
{
  int value;
  if(Serial.available())
  {
    delay(50);
    while(Serial.available() >0)
    {
      value=Serial.read();
      if(value=='1'){digitalWrite(13,HIGH);}
      else if (value=='0') {digitalWrite (13,LOW);
      }
    }
  }
}