How to Use I2C LCD with Arduino: Simple Guide and Example

To use an I2C LCD with Arduino, connect the LCD's SDA and SCL pins to Arduino's SDA (A4) and SCL (A5) pins, then use the LiquidCrystal_I2C library to control the display. Initialize the LCD with its I2C address and call functions like lcd.print() to show text.

Syntax

The basic syntax to use an I2C LCD with Arduino involves including the LiquidCrystal_I2C library, creating an LCD object with the I2C address and size, initializing it, and then using methods to control the display.

• #include <LiquidCrystal_I2C.h>: Includes the library for I2C LCD control.
• LiquidCrystal_I2C lcd(address, cols, rows);: Creates an LCD object with the I2C address and display size.
• lcd.init();: Initializes the LCD.
• lcd.backlight();: Turns on the LCD backlight.
• lcd.print("text");: Prints text on the LCD.

arduino

#include <LiquidCrystal_I2C.h>

// Set the LCD address to 0x27 for a 16 chars and 2 line display
LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  lcd.init();          // Initialize the LCD
  lcd.backlight();     // Turn on the backlight
  lcd.print("Hello"); // Print text
}

void loop() {
  // Nothing here
}

Example

This example shows how to display "Hello, World!" on the first line and "I2C LCD Demo" on the second line of a 16x2 I2C LCD connected to an Arduino.

arduino

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

LiquidCrystal_I2C lcd(0x27, 16, 2); // Address 0x27, 16 columns, 2 rows

void setup() {
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);          // Set cursor to column 0, row 0
  lcd.print("Hello, World!");  // Print first line
  lcd.setCursor(0, 1);          // Set cursor to column 0, row 1
  lcd.print("I2C LCD Demo");  // Print second line
}

void loop() {
  // No repeated actions needed
}

Output

LCD displays:
Hello, World!
I2C LCD Demo

Common Pitfalls

Common mistakes when using I2C LCD with Arduino include:

• Using the wrong I2C address. Use an I2C scanner sketch to find the correct address.
• Not connecting SDA and SCL pins correctly (Arduino Uno uses A4 for SDA and A5 for SCL).
• Forgetting to call lcd.init() and lcd.backlight().
• Not installing the LiquidCrystal_I2C library or using an incompatible version.

arduino

// Wrong I2C address example
// LiquidCrystal_I2C lcd(0x3F, 16, 2); // May not work if address is 0x27

// Correct way after scanning
LiquidCrystal_I2C lcd(0x27, 16, 2);

Quick Reference

Function	Description
lcd.init()	Initializes the LCD display
lcd.backlight()	Turns on the LCD backlight
lcd.noBacklight()	Turns off the LCD backlight
lcd.clear()	Clears the display
lcd.setCursor(col, row)	Sets the cursor position
lcd.print(text)	Prints text at the current cursor position

Key Takeaways

Connect SDA and SCL pins of the I2C LCD to Arduino's A4 and A5 pins respectively.

Use the LiquidCrystal_I2C library and initialize the LCD with the correct I2C address.

Always call lcd.init() and lcd.backlight() before printing text.

Use an I2C scanner sketch to find your LCD's correct I2C address if unsure.

Check wiring and library installation to avoid common connection issues.