// blinking led operated by PC
int LED = 3;
int value;

void setup()
{
  Serial.begin(9600);
  Serial.println("start");
  pinMode(LED, OUTPUT);
}

void loop()
{
  value = Serial.read();

  if (value == '1') {digitalWrite(LED, HIGH);}
  else if (value == '0') {digitalWrite(LED, LOW);}
}