Published August 27, 2026

HD44780U LCD with Arduino: 4-Bit Interface, Custom Character

Learn how to interface a classic Hitachi HD44780U-compatible 16×2 character LCD with an Arduino Uno using only six GPIO pins. This project c

IntermediateWork in progress22

HD44780U LCD with Arduino: 4-Bit Interface, Custom Character

Things used in this project

Hardware components

Arduino Uno Rev3

Microcontroller

HD44780U

Character display

10 kΩ potentiometer

LCD contrast adjustment

Breadboard

Prototyping

Male-to-male jumper wires

Connections

USB cable for Arduino Uno

Programming and power

5 V power source

LCD/Arduino supply

Software apps and online services

Arduino IDE

Write and upload firmware

Arduino LiquidCrystal Library

Control the HD44780-compatible LCD

Serial Monitor

Debug and monitor Arduino output

Fritzing

Optional: create the wiring diagram

Hand tools and fabrication machines

Wire cutter

Wire stripper

Small screwdriver

Soldering iron (generic)

Solder

Digital multimeter

Breadboard jumper wire tool

Story

Introduction

The Hitachi HD44780U is one of the most important LCD controller architectures in the history of embedded electronics. Even though modern projects often use OLED or TFT displays, HD44780-compatible character LCDs are still useful for prototypes, industrial equipment, test instruments, development boards, and simple user interfaces.

A typical 16×2 LCD provides 16 characters on each of two rows. The display communicates with a microcontroller through a parallel interface.

The interface can operate in either 8-bit or 4-bit mode.

For a small Arduino project, 4-bit mode is usually more convenient because it reduces the number of required GPIO connections. The HD44780U datasheet documents the 4-bit initialization sequence and the use of DB4–DB7 for data transfer.

In this project, we will connect an HD44780U-compatible 16×2 LCD to an Arduino Uno and operate it in 4-bit mode.

Why Use 4-Bit Mode?

An LCD in 8-bit mode requires eight data lines:

DB0–DB7

In addition, the controller needs:

That means the interface can consume a significant number of MCU GPIO pins.

In 4-bit mode, only:

are used for data.

Together with:

the Arduino needs only six digital output pins when R/W is permanently tied to ground.

This is also the basic configuration used by the Arduino LiquidCrystal library examples.

Understanding the LCD Pins

A typical 16-pin HD44780-compatible LCD module uses the following interface:

Pin 1: VSS -- Ground

Pin 2: VDD -- Supply voltage

Pin 3: VO -- Contrast voltage

Pin 4: RS -- Register Select

Pin 5: R/W -- Read/Write

Pin 6: E -- Enable

Pin 7: DB0 -- Data bit 0

Pin 8: DB1 -- Data bit 1

Pin 9: DB2 -- Data bit 2

Pin 10: DB3 -- Data bit 3

Pin 11: DB4 -- Data bit 4

Pin 12: DB5 -- Data bit 5

Pin 13: DB6 -- Data bit 6

Pin 14: DB7 -- Data bit 7

Pin 15: A -- Backlight anode*

Pin 16: K -- Backlight cathode*

* Backlight implementation varies between LCD modules, so check the module datasheet before applying power.

In 4-bit mode, DB0–DB3 are not connected.

Code

                    Arduino Uno
                +------------------+
                |                  |
        +5V ----| 5V           D12 |---------- RS
        GND ----| GND          D11 |---------- E
                |               D5 |---------- DB4
                |               D4 |---------- DB5
                |               D3 |---------- DB6
                |               D2 |---------- DB7
                +------------------+
                                     
                              HD44780U LCD
                         +--------------------+
             GND --------| 1  VSS             |
             +5V --------| 2  VDD             |
                         |                    |
 Pot wiper --------------| 3  VO              |
 Arduino D12 ------------| 4  RS              |
 GND --------------------| 5  R/W             |
 Arduino D11 ------------| 6  E               |
                         |                    |
 NC ---------------------| 7  DB0             |
 NC ---------------------| 8  DB1             |
 NC ---------------------| 9  DB2             |
 NC ---------------------| 10 DB3             |
 Arduino D5 -------------| 11 DB4             |
 Arduino D4 -------------| 12 DB5             |
 Arduino D3 -------------| 13 DB6             |
 Arduino D2 -------------| 14 DB7             |
                         |                    |
 +5V / module-specific --| 15 A               |
 GND / module-specific --| 16 K               |
                         +--------------------+

             10 kΩ Contrast Potentiometer

                  +5V
                   |
                [ POT ]
                   |
                   +---------- VO
                   |
                  GND

#include <LiquidCrystal.h>

// HD44780U-compatible LCD
// RS, E, D4, D5, D6, D7
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

// Custom character: small arrow
byte arrowChar[8] = {
  B00000,
  B00100,
  B00110,
  B11111,
  B00110,
  B00100,
  B00000,
  B00000
};

void setup() {
  Serial.begin(9600);

  // Initialize a 16x2 LCD
  lcd.begin(16, 2);

  // Create custom character in CGRAM
  lcd.createChar(0, arrowChar);

  lcd.clear();

  lcd.setCursor(0, 0);
  lcd.print("HD44780U LCD");

  lcd.setCursor(0, 1);
  lcd.print("4-BIT MODE");

  Serial.println("HD44780U LCD test started.");
}

void loop() {

  delay(2000);

  // Demonstrate cursor positioning
  lcd.clear();

  lcd.setCursor(0, 0);
  lcd.print("Arduino Uno");

  lcd.setCursor(0, 1);
  lcd.print("LCD Controller");

  delay(2000);

  // Demonstrate custom character
  lcd.clear();

  lcd.setCursor(0, 0);
  lcd.write(byte(0));
  lcd.print(" Custom Char");

  lcd.setCursor(0, 1);
  lcd.print("HD44780U");

  delay(2000);

  // Demonstrate scrolling
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("4-bit parallel");

  lcd.setCursor(0, 1);
  lcd.print("LCD interface");

  delay(1000);

  for (int i = 0; i < 6; i++) {
    lcd.scrollDisplayLeft();
    delay(300);
  }

  delay(1000);

  for (int i = 0; i < 6; i++) {
    lcd.scrollDisplayRight();
    delay(300);
  }
}

Credits

Robert Fletcher

21 projects • 1 follower

Senior semiconductor engineer at AVAQ Semiconductor. With extensive experience in electronic components, supply chain solutions & sourcing.

HD44780U LCD with Arduino: 4-Bit Interface, Custom Character

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Introduction

Why Use 4-Bit Mode?

Understanding the LCD Pins

Schematics

HD44780U schematics

Code

Schematics

Code

Credits

Robert Fletcher

Comments

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HD44780U LCD with Arduino: 4-Bit Interface, Custom Character

HD44780U LCD with Arduino: 4-Bit Interface, Custom Character

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Introduction

Why Use 4-Bit Mode?

Understanding the LCD Pins

Schematics

HD44780U schematics

Code

Schematics

Code

Credits

Robert Fletcher

Comments

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