How to Connect LCD to Arduino?

 Connecting an LCD (Liquid Crystal Display) to an Arduino is a common task for displaying data. The most popular type is the 16x2 Character LCD, which can be interfaced in 4-bit or 8-bit mode (4-bit is more common to save pins).

Here’s a step-by-step guide:

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1. Components Needed

• Arduino board (Arduino Uno, Arduino Nano, etc.)

• 16x2 LCD (HD44780-compatible)

• Potentiometer (10kΩ) (for contrast adjustment)

• Breadboard & jumper wires

• 220Ω resistor (for backlight, if needed)

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2. Wiring (4-Bit Mode – Recommended)

This method uses 6 Arduino pins (4 data + 2 control).

LCD Pin	Arduino Pin	Description
VSS (GND)	GND	Ground
VDD (VCC)	5V	Power
VO (Contrast)	Potentiometer middle pin	Adjust contrast
RS (Register Select)	D7	HIGH = Data, LOW = Command
RW (Read/Write)	GND	Set to GND (write mode)
E (Enable)	D6	Clock pulse to latch data
D4 (Data 4)	D5	Data bit 4
D5 (Data 5)	D4	Data bit 5
D6 (Data 6)	D3	Data bit 6
D7 (Data 7)	D2	Data bit 7
A (Backlight +)	5V via 220Ω resistor	Anode (+)
K (Backlight –)	GND	Cathode (–)

Contrast Adjustment

• Connect VO to the middle pin of a 10kΩ potentiometer (other pins to 5V and GND).

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3. Arduino Code (Using LiquidCrystal Library)

cpp

#include <LiquidCrystal.h>

// Initialize LCD (RS, E, D4, D5, D6, D7)
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);

void setup() {
  lcd.begin(16, 2);  // Set up 16x2 LCD
  lcd.print("Hello, Arduino!");  // Print a message
}

void loop() {
  lcd.setCursor(0, 1);  // Move to 2nd row
  lcd.print("Time: ");
  lcd.print(millis() / 1000);  // Display seconds
}

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4. Alternative (I2C LCD – Fewer Wires)

If you have an I2C LCD module, it only needs 4 wires (GND, VCC, SDA, SCL).

Wiring

I2C LCD Pin	Arduino Pin
GND	GND
VCC	5V
SDA	A4 (Uno) / SDA (Nano)
SCL	A5 (Uno) / SCL (Nano)

Code (Using LiquidCrystal_I2C Library)

cpp

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);  // Address 0x27, 16x2 LCD

void setup() {
  lcd.init();  // Initialize LCD
  lcd.backlight();  // Turn on backlight
  lcd.print("Hello, I2C LCD!");
}

void loop() {
  lcd.setCursor(0, 1);
  lcd.print("Millis: ");
  lcd.print(millis() / 1000);
}

Note: The I2C address may vary (common: 0x27 or 0x3F). Use an I2C scanner if the LCD doesn’t work.

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5. Troubleshooting

Issue	Solution
Blank display	Adjust contrast (VO) with potentiometer
Garbled text	Check wiring (especially data pins)
No backlight	Check 220Ω resistor on backlight (+)
I2C LCD not working	Verify I2C address (0x27/0x3F)

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Final Recommendations

• For simplicity: Use I2C LCD (only 4 wires).

• For learning: Try 4-bit mode first.

• For custom characters: Use lcd.createChar().