#include <Wire.h>void setup(){  Wire.begin(); // join i2c bus (address optional for master)}byte x = 0;void loop(){  Wire.beginTransmission(4); // transmit to device #4  Wire.write("x is ");        // sends five bytes  Wire.write(x);              // sends one byte    Wire.endTransmission();    // stop transmitting  x++;  delay(500);}

#include <Wire.h>void setup(){  Serial.begin(9600);           // start serial for output  while(!Serial);  Wire.begin(4);                // join i2c bus with address #4  Wire.onReceive(receiveEvent); // register event  }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){  Serial.println("REQ");  while(1 < Wire.available()) // loop through all but the last  {    char c = Wire.read(); // receive byte as a character    Serial.print(c);         // print the character  }  int x = Wire.read();    // receive byte as an integer  Serial.println(x);         // print the integer}

#include <Wire.h>void setup() {  Wire.begin();        // join I2C bus (address optional for master)  Serial.begin(9600);  // start serial for output}void loop() {  Wire.requestFrom(16, 6);    // request 6 bytes from slave device #8  while (Wire.available()) { // slave may send less than requested    Serial.write(Wire.read());         // print the character  }  Serial.println();  delay(500);}

#include <Wire.h>void setup() {  Wire.begin(16);                // join I2C bus with address #8  Wire.onRequest(requestEvent); // register event}void loop() {  delay(1);}// function that executes whenever data is requested by master// this function is registered as an event, see setup()void requestEvent() {  Wire.write("hello "); // respond with message of 6 bytes  // as expected by master}