I2C

I2C inter micro controller communication

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

Second experiment, Succeeded :-)

I2C connection between one master Arduino & one Slave Arduino over a serial clock pin (SCL, pin number 4 in the picture down here, YELLOW wire) that the Arduino pulses at a regular interval, and a serial data pin (SDA, Pin number 5 in the picture down here, RED wire) over which data is sent between the two devices. Also make sure that the grounds are connected together.

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