Interfacing a 16×2 I2C LCD with ESP32: Hardware Connections and Firmware Implementation

ByHaneen ✓February 24, 2026

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16 x 2 LCD Display connection to ESP32

This article presents a structured technical guide for interfacing a 16×2 alphanumeric LCD module equipped with an I2C backpack to the ESP32 microcontroller. The paper describes hardware architecture, I2C communication fundamentals, pin configuration, firmware implementation using the Arduino framework, and troubleshooting methodology. The objective is to provide a concise yet technically rigorous reference suitable for embedded systems learners and practitioners.

I. Introduction

Display modules are essential in embedded systems for real-time monitoring and user interaction. The 16×2 alphanumeric LCD is widely used due to its simplicity, low cost, and reliability. Traditionally, it requires multiple GPIO pins; however, by integrating an I2C backpack (typically based on the PCF8574 I/O expander), communication is reduced to two data lines.

The ESP32 microcontroller, developed by Espressif Systems, provides built-in I2C support and flexible GPIO routing, making it well suited for such applications.

This paper demonstrates the hardware connection and software implementation required to display text on a 16×2 LCD via I2C using the ESP32.

II. System Architecture

Hardware Components

ESP32 DEVELOPMENT Board
16 x 2 LCD Module with I2C Backpack
Jumper Wires
USB Cable for Programming

Communication Protocol: I2C

Inter-Integrated Circuit (I2C) is a synchronous serial communication protocol that uses two bidirectional lines:

SDA → GPIO 21
SCL → GPIO 22

III. Hardware Interfacing

Pin Configuration

LCD I2C Pin	ESP32 Pin
GND	GND
VCC	5V
SDA	GPIO 21
SCL	GPIO 22

Note: Most I2C LCD modules operate at 5V. The ESP32 I2C lines are 3.3V tolerant and typically function correctly due to onboard pull-up resistors on the LCD backpack.

IV. Software Implementation

A. Development Environment

Arduino IDE
ESP32 Board Package Installed
LiquidCrystal_I2C Library

Commonly used library:
LiquidCrystal_I2C (compatible with PCF8574 modules)

B. Firmware Code

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

// Initialize LCD (address, columns, rows)
LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
Wire.begin(21, 22); // Explicitly define SDA and SCL
lcd.init();
lcd.backlight();

lcd.setCursor(0, 0);
lcd.print("Hello World!");

lcd.setCursor(0, 1);
lcd.print("ESP32 I2C LCD");
}

void loop() {
// No repeated operation required
}

This article presented a structured technical procedure for interfacing a 16×2 I2C LCD with the ESP32. By leveraging the I2C protocol, GPIO usage is minimized while maintaining reliable display functionality. The presented firmware and hardware configuration provide a scalable foundation for embedded monitoring systems, IoT dashboards, and real-time data visualization applications.

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Tags: Electronics robotics

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