// I2C Master
// Push a button connected to the master controller
// lights an LED connected to the slave

// Andrew Sleigh
// 2018-04-26

#include <Wire.h>

const int ledPin =  13;      // the number of the LED pin
int  x = 0;

void setup() {
  
  // initialize the LED pin as an output:
  pinMode(ledPin, OUTPUT);
  digitalWrite(ledPin, LOW);

  Wire.begin(7);                // join i2c bus with address #7

  // Attach a function to trigger when something is received.
  // From http://www.instructables.com/id/I2C-between-Arduinos/
  Wire.onReceive(receiveEvent);
  
}

void receiveEvent(int bytes) {
   x = Wire.read();    // read one character from the I2C
}

void loop() {

  if (x == 0) {
      // received an OFF command 
      digitalWrite(ledPin, LOW);
  } 

  if (x == 1) {
    // received an ON command 
      digitalWrite(ledPin, HIGH);
  } 

}