🧠 4-Bit LCD Interfacing with Arduino UNO 📖 Overview

This project demonstrates how to interface a 16x2 LCD display with an Arduino UNO using 4-bit communication mode. The 4-bit mode reduces pin usage by sending data in two nibbles (4 bits each), allowing you to save Arduino I/O pins for other peripherals.

⚙️ Hardware Requirements

Arduino UNO

16x2 LCD Display

Jumper Wires

Breadboard

Potentiometer (for contrast adjustment)

🔌 Pin Connections LCD Pin Description Arduino Pin RS Register Select D3 RW Read/Write D4 EN Enable D5 D4 Data Bit 4 D10 D5 Data Bit 5 D11 D6 Data Bit 6 D12 D7 Data Bit 7 D13 💻 Arduino Code const int RS = 3; const int RW = 4; const int EN = 5; const int D4 = 10; const int D5 = 11; const int D6 = 12; const int D7 = 13;

void printdata(unsigned char data) { if(data&0x10 == 0x10) { digitalWrite(D4,HIGH); } else { digitalWrite(D4,LOW); }

if(data&0x20 == 0x20) { digitalWrite(D5,HIGH); } else { digitalWrite(D5,LOW); }

if(data&0x40 == 0x40) { digitalWrite(D6,HIGH); } else { digitalWrite(D6,LOW); }

if(data&0x80 == 0x80) { digitalWrite(D7,HIGH); } else { digitalWrite(D7,LOW); } }

void lcd_data(unsigned char data) { printdata(data&0x0F); digitalWrite(RS,HIGH); digitalWrite(RW,LOW); digitalWrite(EN,HIGH); delay(2); digitalWrite(EN,LOW);

printdata(data<<4); digitalWrite(RS,HIGH); digitalWrite(RW,LOW); digitalWrite(EN,HIGH); delay(2); digitalWrite(EN,LOW); }

void lcd_command(unsigned char command) { printdata(command&0x0F); digitalWrite(RS,LOW); digitalWrite(RW,LOW); digitalWrite(EN,HIGH); delay(2); digitalWrite(EN,LOW);

printdata(command<<4); digitalWrite(RS,LOW); digitalWrite(RW,LOW); digitalWrite(EN,HIGH); delay(2); digitalWrite(EN,LOW); }

void lcd_string(unsigned char str[], unsigned char num) { for(unsigned char i=0; i<num; i++) { lcd_data(str[i]); } }

void lcd_initialise() { lcd_command(0x28); lcd_command(0x0C); lcd_command(0x06); lcd_command(0x01); }

void setup() { pinMode(RS,OUTPUT); pinMode(RW,OUTPUT); pinMode(EN,OUTPUT);

pinMode(D4,OUTPUT); pinMode(D5,OUTPUT); pinMode(D6,OUTPUT); pinMode(D7,OUTPUT);

lcd_initialise(); }

void loop() { lcd_command(0x80); lcd_string("Hello",5); lcd_command(0xC0); lcd_string("World",5); }

📺 Output Hello World

🧩 Key Concepts

Bitwise operations for pin control

4-bit LCD communication protocol

Manual LCD command and data transfer

💡 Future Enhancements

Display sensor data (Temperature, Humidity, etc.)

Implement scrolling or blinking text

Integrate with IoT or serial input