#include <Wire.h>
#define ledPin 1

void setup() {
  pinMode(ledPin,OUTPUT);
  Wire.begin(9);                // join i2c bus with address #9
  Wire.onReceive(receiveEvent); // register event
}

void loop() {
  delay(10);
}

// function that executes whenever data is received from master
// this function is registered as an event, see setup()
void receiveEvent(int howMany) {
  while (0 < Wire.available()) { // loop through all but the last
    char c = Wire.read(); // receive byte as a character
    digitalWrite(ledPin, c);
  }
}