char val;
const int ledPin = 2;

void setup() 
{
  pinMode(ledPin, OUTPUT); // Set pin as OUTPUT
  digitalWrite(ledPin,HIGH);
  //initialize serial communications at a 9600 baud rate
  Serial.begin(9600);
  Serial.println("START");
}

 
void loop()
{
  if (Serial.available() > 0) { // If data is available to read,
    val = Serial.read(); // read it and store it in val

    if(val == '1') //if we get a 1
    {
      Serial.println("Włączamy");
      digitalWrite(ledPin, LOW); 
    }
    else if ( val == '2'){
      Serial.println("Wyłączamy");
      digitalWrite(ledPin, HIGH);
    }
  }
}