i2c communication and response

master.ino

// Wire Master Writer
// by Nicholas Zambetti <http://www.zambetti.com>

// 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 <Wire.h>

void setup() {
  Wire.begin(); // join i2c bus (address optional for master)
    Serial.begin(9600);  // start serial for output

}

byte x = 0;

void loop() {
  Wire.beginTransmission(8); // transmit to device #8
  Wire.write("x is ");        // sends five bytes
  Wire.write(x);              // sends one byte
  Wire.endTransmission();    // stop transmitting
  
  
  Wire.requestFrom(8, 6);    // request 6 bytes from slave device #8
  while (Wire.available()) { // slave may send less than requested
    char c = Wire.read(); // receive a byte as character
    Serial.print(c);         // print the character
  }
      Serial.println();         // print the character

  x++;
  delay(500);
}

slave.ino

// Wire Slave Receiver
// by Nicholas Zambetti <http://www.zambetti.com>

// 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 <Wire.h>

void setup() {
  Wire.begin(8);                // join i2c bus with address #8
  Wire.onReceive(receiveEvent); // register event
  Wire.onRequest(requestEvent); // register event

  Serial.begin(9600);           // start serial for output
}

void loop() {
  delay(100);
}
int lastx;

// function that executes whenever data is requested by master
// this function is registered as an event, see setup()
void requestEvent() {
    Wire.write("x is ");        // sends five bytes
  Wire.write(lastx);
//  Wire.write("hello "); // respond with message of 6 bytes
  // as expected by master
}

// 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.read(); // receive byte as a character
    Serial.print(c);         // print the character
  }
  int x = Wire.read();    // receive byte as an integer
  lastx=x;
  Serial.println(x);         // print the integer
}