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LCD I2C

LCD

Introduction​

The 16×2 LCD (Liquid Crystal Display) is a widely used alphanumeric display module capable of showing 16 characters per line on 2 lines. It is based on the Hitachi HD44780 controller, which provides a simple command-based interface for displaying characters, symbols, and custom graphics.

To reduce the number of GPIO pins required for communication, the LCD is often connected through an I²C I/O expander, typically the PCF8574 chip. This configuration allows the LCD to communicate with the microcontroller using only two wires — SDA (Serial Data) and SCL (Serial Clock) — instead of the usual 6 to 8 parallel data and control lines.

The PCF8574 acts as a bridge between the microcontroller’s I²C bus and the LCD’s parallel interface, providing:

  • Pin saving
  • Simpler wiring
  • Easy software control
  • Without it, you would need many more GPIO pins and complex wiring to operate the LCD.

Pin Configuration​

LCD PinGlyph-C3
VCCPower Supply
GNDGND
SDAGPIO 21
SCLGPIO 22

Features​

  • Uses I²C communication — only two wires (SDA and SCL) are required.
  • Saves microcontroller pins — reduces pin usage from 8 (parallel) to 2.
  • Compatible with the HD44780 LCD controller.
  • Based on PCF8574 I/O expander for serial-to-parallel data conversion.
  • Built-in LED backlight for better visibility.
  • Adjustable contrast using the onboard potentiometer.
  • Operates on 3.3V or 5V, suitable for most microcontrollers (Arduino, ESP32, ESP8266, Raspberry Pi).
  • Displays 16 characters × 2 lines (total 32 characters).

Typical Applications​

  • Embedded system displays — show system status or information.
  • Sensor data monitoring — display temperature, humidity, voltage, etc.
  • Industrial control panels — parameter and status display.
  • IoT devices — display device data or connection status.
  • Educational and training projects — for learning I²C and LCD interfacing.
  • Digital meters — voltage, current, and frequency measurement displays.
  • Home automation systems — display time, mode, or device state.

Step 1: Hardware Required​

  1. GLYPH
  2. LCD Display
  3. PCF-8574

Step 2: Circuit Diagram​

Step 3: Code Setup​

  1. Open Arduino IDE.
  2. Make sure to install the library
  3. Copy and paste the following code into the Arduino IDE
#include <Wire.h>
#include <LiquidCrystal_I2C.h> // https://www.arduinolibraries.info/libraries/liquid-crystal-i2-c

// Initialize LCD: I2C address 0x27, 16 columns, 2 rows
LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  lcd.init();          // Initialize the LCD
  lcd.backlight();     // Turn ON backlight

  // Print text
  lcd.setCursor(0, 0);  
  lcd.print("Hello");
  lcd.setCursor(0, 1);
  lcd.print("PCBCUPID");
}

void loop() {
  // Static display - nothing needed
}

Step 4: Upload the Code​

  1. Connect the Board
  • Connect your GLYPH board to your computer
  1. Select the Board and Port

Do the following settings in your Arduino IDE,

  • Tools > Board > esp32 > Pcbcupid Glyph S3
warning

For the Pcbcupid Glyph S3 to appear under Tools > Board > esp32, the esp32 board version installed in the Arduino IDE should be greater or equal to 3.1.0.

  • Tools > Port and select the port connected to your GLYPH.
  • Tools > USB CDC on Boot > Enabled
warning

If USB CDC on BOOT not enabled, you won't be seeing any serial data on Arduino IDE.

  1. Upload the Code

    • Click the upload button (➡️ icon) or use the shortcut CRTL + U in Arduino IDE to upload the code to the board.

Step 5: Observe Output on Serial Monitor​

LCD