/*-----------------------------------------------------------------
 *           Serial communication with the Arduino 
 *   (Like, for example - receiving data from Raspberry Pi)
 * Setup: Wire an LED from digital 6 thru 330 ohm resistor to gnd
 -----------------------------------------------------------------*/
 
char inData;        // variable for storing received serial data
int convertData;    // variable or storing data converted into integers
int ledPin = 6;     // variable for LED pin number

 void setup(){
    Serial.begin(9600);
    pinMode(ledPin, OUTPUT);        // set pin Mode for lighting LED
 }

void loop(){

    if (Serial.available() > 0){    // if serial data (RPi to Arduino)
       inData = Serial.read();      // read it, store in inData
       delay(15);
       convertData = (int)inData - 48; // Convert char into an integer
       Serial.println(convertData);    // print it in the serial monitor
        if(convertData == 1) {         // If data is a "1"
          digitalWrite(ledPin, HIGH);  // light LED, 
        } else {                       // otherwise
          digitalWrite(ledPin, LOW);   // off LED
      }
    }
}