Notes

#include <Wire.h>
#include <LCD.h>
#include <LiquidCrystal_I2C.h>

#define I2C_ADDR 0x27 // Define I2C Address where the PCF8574A is
#define BACKLIGHT_PIN 3
#define En_pin 2
#define Rw_pin 1
#define Rs_pin 0
#define D4_pin 4
#define D5_pin 5
#define D6_pin 6
#define D7_pin 7

int n = 1;

LiquidCrystal_I2C lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin);

void setup()
{
lcd.begin (20,4);

// Switch on the backlight
lcd.setBacklightPin(BACKLIGHT_PIN,POSITIVE);
lcd.setBacklight(HIGH);
lcd.home (); // go home

lcd.print("SainSmart I2C tester");
lcd.setCursor ( 0, 1 ); // go to the 2nd line
lcd.print("F Malpartida library");
lcd.setCursor ( 0, 2 ); // go to the third line
lcd.print("Test & demonstration");
lcd.setCursor ( 0, 3 ); // go to the fourth line
lcd.print("Iteration No: ");
}

void loop()
{
// Backlight on/off every 3 seconds
lcd.setCursor (14,3); // go col 14 of line 3
lcd.print(n++,DEC);
lcd.setBacklight(LOW); // Backlight off
delay(3000);
lcd.setBacklight(HIGH); // Backlight on
delay(3000);
}