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Interfacing 20x4 LCD with Arduino

20x4 LCD Display

A 20x4 LCD is a character display that can show 20 characters per line across 4 lines. It's commonly used in DIY electronics, embedded systems, and Arduino projects for displaying real-time information like sensor data, messages, or menus.

Working Principle of 20x4 LCD

The 20x4 LCD operates using a controller (typically HD44780) which receives digital signals from the Arduino. These signals are interpreted as characters and displayed on the screen. The display uses liquid crystals to block or allow light, forming visible text.

Types of LCD Interfaces

Parallel Interface (Standard)

  • Connect RS, EN, and D4–D7 pins to Arduino.
  • Send commands and data using digitalWrite().
  • Use a potentiometer to adjust the contrast.

I2C Interface (with I2C Module)

  • Attach I2C module to the LCD.
  • Connect SDA and SCL pins to Arduino A4 and A5 (on UNO).
  • Communicate using LiquidCrystal_I2C library.

Requirements

1. Arduino Uno (or compatible board)

2. 20x4 LCD Display

3. 10K Potentiometer

4. Jumper wires

Pin Configuration of 20x4 LCD (Parallel)

LCD Pinout

  • VSS: Connect to GND
  • VDD: Connect to +5V
  • VO: Connect to potentiometer center pin (contrast)
  • RS: Register Select (connect to digital pin)
  • RW: Read/Write (connect to GND for write)
  • EN: Enable (connect to digital pin)
  • D4–D7: Data lines (connect to digital pins)
  • A/K: Anode & Cathode for backlight (connect via resistor)

Wiring the 20x4 LCD to Arduino

To wire the 20x4 LCD in parallel mode, connect the data and control pins (RS, EN, D4-D7) to digital pins on the Arduino. Include a 10K potentiometer for contrast and optionally a resistor for backlight control. For simpler wiring, use an I2C module.

Algorithm

  1. Connect the LCD to Arduino

    • Use jumper wires to connect RS, EN, D4-D7 to digital pins.
    • Wire power, ground, and potentiometer for contrast adjustment.
    • Optionally add a resistor to control backlight brightness.

  2. Install Required Library

    • Open Arduino IDE.
    • Go to Library Manager and install 'LiquidCrystal' library.

  3. Write the Code

    • Include <LiquidCrystal.h> in your sketch.
    • Define the pin connections in LiquidCrystal lcd(...) object.
    • Use lcd.begin(20, 4) in setup() and lcd.print() in loop().

  4. Upload and Test

    • Upload the sketch to Arduino.
    • Observe the displayed text on the LCD screen.
    • Adjust the contrast using the potentiometer if needed.

Experiment of Code

5. Breadboard (optional)

Arduino Code

1#include <LiquidCrystal.h>
2
3// RS, E, D4, D5, D6, D7
4LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
5
6void setup() {
7  lcd.begin(20, 4); // 20 columns, 4 rows
8  lcd.setCursor(0, 0);
9  lcd.print("20x4 LCD Display");
10  lcd.setCursor(0, 1);
11  lcd.print("Line 2 text here");
12  lcd.setCursor(0, 2);
13  lcd.print("Line 3 content");
14  lcd.setCursor(0, 3);
15  lcd.print("Line 4 goes here");
16}
17
18void loop() {
19  // Nothing required here
20}
21

Applications of 20x4 LCDs

  • Weather monitoring systems
  • Digital clocks and timers
  • Home automation dashboards
  • Sensor data display
  • Menu-driven interfaces for projects
  • Educational electronics kits

Conclusion

Connecting a 20x4 LCD to Arduino is a great way to visualize real-time data in your projects. With easy setup and support from the LiquidCrystal library, it's an ideal display solution for both beginners and advanced makers.