>I2C inter micro controller communication

First experiment, failed !!! The problem : Grounds were not connected together !!!

Second experiment, Succeeded :-)

Master Writer Code – Program for Arduino 1

// Wire Master Writer// by Nicholas Zambetti 

// Demonstrates use of the Wire library// Writes data to an I2C/TWI slave device// Refer to the "Wire Slave Receiver" example for use with this

// Created 29 March 2006

// This example code is in the public domain.

#include 

void setup(){  Wire.begin(); // join i2c bus (address optional for master)}

byte x = 0;

void loop(){  Wire.beginTransmission(4); // transmit to device #4  Wire.send("x is ");        // sends five bytes  Wire.send(x);              // sends one byte    Wire.endTransmission();    // stop transmitting

  x++;  delay(500);}

Slave Receiver Code – Program for Arduino 2

// Wire Slave Receiver// by Nicholas Zambetti 

// Demonstrates use of the Wire library// Receives data as an I2C/TWI slave device// Refer to the "Wire Master Writer" example for use with this

// Created 29 March 2006

// This example code is in the public domain.

#include 

void setup(){  Wire.begin(4);                // join i2c bus with address #4  Wire.onReceive(receiveEvent); // register event  Serial.begin(9600);           // start serial for output}

void loop(){  delay(100);}

// function that executes whenever data is received from master// this function is registered as an event, see setup()void receiveEvent(int howMany){  while(1 < Wire.available()) // loop through all but the last  {    char c = Wire.receive(); // receive byte as a character    Serial.print(c);         // print the character  }  int x = Wire.receive();    // receive byte as an integer  Serial.println(x);         // print the integer}

Source : http://arduino.cc/en/Tutorial/MasterWriter