Arduino/LCD Display

This page covers how to use a SainSmart LCD 2004 display with an Arduino.

Overview

So far we've covered some really simple circuits with single components. We're not doing a whole lot with the voltages in our system, or with the microcontroller. This project will introduce a more advanced output device for the Arduino, namely, an LCD display for printing simple text messages.

The LCD Display

To begin with, we can note a couple of things about the LCD display:

First, the display has its own microcontroller on-board, meaning it has hardware dedicated to turning voltage signals on the microcontroller board (coming from the Arduino) into the right output signals for its LCD display. All of that circuitry and the details of connecting an Arduino to the Sainsmart LCD 2004 are covered on the Sainsmart website (scroll down to the documents section, they link to a zip file that contains a bunch of example sketches and

What is I2C?

We've already noticed there's a separate integrated circuit onboard the LCD display. That means we'll be using something called I2C, which stands for Inter-Integrated Circuit. It's a way for integrated circuits (microprocessors) to talk to each other.

I2C Pins on Arduino

In order to use I2C, you'll need to use special I2C pins onboard the Arduino. There are two wires - one is labeled SDA (System Data) and the other is labeled SCL (System Clock). They're labeled SDA and SCL on the Sainsmart's board, so that side will be clear. But which pins they'll plug into on the Arduino board depends on the type of board.

This site lists the SDA/SCL pins for a couple of boards, and I've added a few:

Board Type	SDA Pin	SCL Pin	Reference
Micro	1	2	Arduino.cc website - Arduino Micro
Uno	A4	A5	An excellent and very thorough I2C example
Leonardo	2	3	Robotic-Controls.com
Mega2560	20	21	Robotic-Controls.com
Due	20	21	Robotic-Controls.com

The Circuit

Breadboard Photo

Here's what the breadboard wiring looks like on the Arduino side:

We have the 5V and ground wires (red and black), and the SDA and SCL wires (green and yellow).

The other side is hooked up in a straightforward way:

Hello World Sainsmart Sketch Code

To display static information on the display, Sainsmart provides the following "Hello World" app:

//YWROBOT
#include <Wire.h> 
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x3F,20,4);  // set the LCD address to 0x3F for a 16 chars and 2 line display

void setup()
{
  lcd.init();                      // initialize the lcd 
  lcd.init();
  // Print a message to the LCD.
  lcd.backlight();
  lcd.setCursor(3,0);
  lcd.print("Hello, world!");
  lcd.setCursor(2,1);
  lcd.print("SainSmart for UNO");
   lcd.setCursor(2,2);
  lcd.print("SainSmart LCM IIC");
   lcd.setCursor(1,3);
  lcd.print("Design By SainSmart");
}

void loop()
{
}

Note that you'll find a couple of different I2C addresses floating around, like 0x20 and 0x27. I'm not sure where people are getting those from, but the 0x3F value comes from Sainsmart's website, and it works right out of the box.