int photocellReading=0; // the analogue reading from the sensor
void setup(void) {
 // put your setup code here, to run once:
 Serial.begin(115200); 
 pinMode(13, INPUT);
}
void loop(void) {
 // put your main code here, to run repeatedly:
 if (Serial.available() > 0)
  {
    photocellReading = Serial.read();
    Serial.print("Received: ");
    Serial.println(photocellReading);
  }
 delay(1000);
}