Sainsmart LCD2004 newbie question - can't get it working

Other Hardware Displays
13

There are a number of things that can go wrong.
I suggest you run this code:
/*
** Example Arduino sketch for SainSmart I2C LCD Screen 16x2
** based on Bitbucket
** by Edward Comer
** LICENSE: GNU General Public License, version 3 (GPL-3.0)
**
** This example uses F Malpartida's NewLiquidCrystal library. Obtain from:
** https://bitbucket.org/fmalpartida/new-liquidcrystal

** Modified - Ian Brennan ianbren at hotmail.com 23-10-2012 to support Tutorial posted to Arduino.cc
** Modified 24/11/15 by Alan Howlett of www.DataTechnologies.co.uk to aid in finding LCD devices on the I2C bus.
** It assumes an LCD might exist on any of the 127 valid addresses and send them a message like "I am on 0x3F".
** If you run this and can't see anything:
** 1. Have a look on Tools, Serial Monitor- do you see a message saying it was found? If not, check your wiring.
** 2. You might need to adjust the contrast screw on the back of the I2C module on your display to see anything!
** Some of this code copied from the I2C_Scanner utility that some kind anonymous person wrote. Thank you, whoever!
*/
#include <Wire.h>
#include <LCD.h>
#include <LiquidCrystal_I2C.h>

#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

void setup()
{
pinMode(13,OUTPUT);
Serial.begin(9600);
}

void loop()
{
// Send a message to every possible LCD display on the I2C bus
for (int address=0; address<127; address++) {
LiquidCrystal_I2C lcd(address,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin);
lcd.begin (20,4); //(How many columns, how many rows) in your display
lcd.setBacklightPin(BACKLIGHT_PIN,POSITIVE);
lcd.setBacklight(HIGH);
lcd.home (); // go to top left position
lcd.print("LCD on 0x");
lcd.print(address, HEX);
lcd.setCursor(0,1);
lcd.print("0x");
lcd.print(address, HEX);
lcd.print(" LCD address");

Wire.beginTransmission(address); //Now check the I2C bus communications
// Wire.write("fred");
int error = Wire.endTransmission(); //Get the error code, if any.

if (error == 0) {
Serial.print("I2C device found at address 0x");
if (address<16)
Serial.print("0");
Serial.println(address,HEX);
}
}
Serial.println("--------------------------------------------------------");
Serial.println("");

digitalWrite(13,LOW);
delay(500);
digitalWrite(13,HIGH);
delay(500);
}

  1. You should be able to see on the serial port whether it has found an I2C device, and
  2. If you adjust the contrast on the LCD display (essential!) you should see the address of the display on the display. Always check the contrast- you usually can't see anything useful until it's adjusted.
  3. Write the I2C address on the back of the display with a permanent marker so you won't forget it!