TWI on the Arduino Mini

/*
 * TWI Test
 * ES
 * 05 April 2008
 *
 * Trying to get TWI to work.  Setup - two arduino minis, one ID6 and one ID7.
 * The same code (with a different hard-coded ID) runs on both minis.
 * ID6 has a pot attached to pin2, and ID7 has a LED attached to pin13.  ID6 sends the pot
 * value over TWI to ID7, which receives it and blinks the LED at a corresponding rate.
 *
 */
 
#include <Wire.h>

int nodeID = 6;    // set the unique ID of the node
int potPin = 2;    // select the input pin for the potentiometer
int ledPin = 13;   // select the pin for the LED
int val = 0;       // variable to store the value coming from the sensor

void setup() {
  pinMode(ledPin, OUTPUT);        // declare the ledPin as an OUTPUT
  Wire.begin(nodeID);             // join i2c bus (address optional for master)
  Wire.onReceive(receiveEvent);   // register event
}

void loop() {
  if (nodeID == 6) {
    val = analogRead(potPin);    // read the value from the sensor
    val = val / 4;               // analogRead gives us 0-1023, we only want 1 byte
    
    Wire.beginTransmission(7); // transmit to device #4
    Wire.send(val);              // sends one byte  
    Wire.endTransmission();    // stop transmitting
  }
  
  if (nodeID == 7) {
    digitalWrite(ledPin, HIGH);  // turn the ledPin on
    delay(val);                  // stop the program for some time
    digitalWrite(ledPin, LOW);   // turn the ledPin off
    delay(val);                  // stop the program for some time
  }
}

// function that executes whenever data is received from master
// this function is registered as an event, see setup()
void receiveEvent(int howMany)
{
  val = Wire.receive();
}