LCD595

An Arduino library for controlling a standard 1602 LCD module using a 74HC595 shift register. This library allows you to display text on the LCD using only 3 Arduino pins (data, clock, latch), freeing up valuable I/O.

📷 Overview

This library drives a 1602 (or compatible) character LCD by sending 4-bit data through a 74HC595 shift register. It minimizes pin usage by shifting out the required bits over SPI-style control.

🛠️ Features

• Minimal wiring — uses only 3 Arduino pins
• Supports standard 1602 LCD commands
• Simple API: begin(), clear(), print(), command()
• Easily expandable (setCursor, createChar, etc.)

📦 Requirements

• Arduino-compatible board (Nano, Uno, Mega, etc.)
• 1602 LCD module (HD44780-compatible)
• 74HC595 shift register
• Arduino IDE

🔌 Wiring

LCD Pin	74HC595 Output	Description
RS	Q0	Register Select
E	Q1	Enable
D4	Q2	Data 4
D5	Q3	Data 5
D6	Q4	Data 6
D7	Q5	Data 7
VSS	GND	Ground
VDD	5V	Power
VO	Potentiometer	Contrast control
R/W	GND	Write only
A/K	5V / GND	Backlight (+/-)

Arduino → 595 connections:

• Data → Arduino pin X (pin 2)

• Clock → Arduino pin Y (pin 4)

• Latch → Arduino pin Z (pin 3)

• Replace X, Y, Z with your actual pin numbers when initializing.

🔧 Installation

1. Download this repo as .zip or clone via Git:

   git clone https://github.com/llcesselx/LCD595.git
   

😵 How to Use

4-Bit Initialization Mode begin Command

According to 1602 LCD Module Datasheets, the initialization sequence recommends giving the LCD at least 40 ms to start up, when the LCD starts up, it starts in 8-bit mode by default. We are only using 4 data pins and want to start the LCD in 4-bit mode. We have to do this manually.

Sending the nibble 0x03 sends the bits 0011 to the LCD three times to ensure the LCD is fully reset. When we send the fourth nibble 0x02, we are sending the bits 0010 which sets it to 4-bit mode. Every program has to start with (your initialization here).begin();

void LCD595::begin() {
    pinMode(_dataPin, OUTPUT);
    pinMode(_clockPin, OUTPUT);
    pinMode(_latchPin, OUTPUT);

    delay(50); // Wait for LCD to power up

    // LCD init sequence (4-bit mode)
    sendNibble(0x03, false);
    delay(5);
    sendNibble(0x03, false);
    delayMicroseconds(150);
    sendNibble(0x03, false);
    sendNibble(0x02, false); // Set 4-bit mode

    // Function set: 4-bit, 2 line, 5x8
    command(0x28);
    // Display ON, cursor OFF, blink OFF
    command(0x0C);
    // Clear display
    command(0x01);
    delay(2);
    // Entry mode set: left to right
    command(0x06);
}