📘 What is an I2C LCD?

An I2C LCD is a Liquid Crystal Display that uses the I2C communication protocol to show text data. It’s widely used in embedded and IoT projects to display information such as temperature, sensor values, time, and status messages.

✅ Key Features:

• Displays text only (not graphics)
• Usually 16×2 (16 characters x 2 lines) or 20×4
• Has an I2C backpack (PCF8574 chip) that allows communication using just 2 pins: SDA (data) and SCL (clock)
• Saves GPIO pins, compared to traditional 6- or 8-pin LCD control

🧰 Components Used

🔌 I2C LCD Pinout and Connection to ESP32

📌 The I2C address is usually 0x27 or 0x3F

🧪 How I2C LCD Works

• The I2C backpack on the LCD uses the PCF8574 chip, which acts as an I/O expander.
• This chip converts 2-wire I2C signals into the parallel signals needed to control the LCD.
• The ESP32 sends commands/data over SDA/SCL, and the chip handles display logic.

⚙️ Operating Principle

• The LCD has two rows: Row 0 and Row 1.
• Each row supports 16 characters (in a 16×2 LCD).
• You control the cursor to set where text appears.
• The LiquidCrystal_I2C library simplifies the process.

🧱 Arduino Setup

🧩 Step 1: Install Required Libraries

In Arduino IDE:

1. Go to Sketch > Include Library > Manage Libraries
2. Search and install:
   • ✅ LiquidCrystal_I2C (by Frank de Brabander or compatible)

💡 LCD Functions Summary

✅ Common Problems & Fixes

🎯 Real-world Applications

HOW TO OPERATE

#include <LiquidCrystal_I2C.h>

#include “DHT.h”

#define DHTPIN 18

#define LIG 2  

LiquidCrystal_I2C lcd(0x27,20,4);

void setup() {

  Serial.begin(9600);

  Serial.println(“DHTxx test!”);

  lcd.init();

lcd.backlight();

  dht.begin();

}

void loop() {

  delay(2000);

  lcd.setCursor(0,0);

  lcd.println(“HELLO IOTWEBPLANET”);

}