> ## Documentation Index
> Fetch the complete documentation index at: https://learn.pcbcupid.com/llms.txt
> Use this file to discover all available pages before exploring further.
> Connect a 16x2 LCD with I2C backpack to a Glyph ESP32 board over two wires and print messages using the LiquidCrystal_I2C Arduino library.
# I2C LCD Display
# LCD I2C
## 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 Pin | Glyph-C3 |
| ------- | ------------ |
| VCC | Power Supply |
| GND | GND |
| SDA | GPIO 21 |
| SCL | GPIO 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
```cpp theme={null}
#include
#include // 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
2. **Select the Board and Port**
Do the following settings in your Arduino IDE,
* `Tools > Board > esp32 > Pcbcupid Glyph S3`
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***
If `USB CDC on BOOT` not enabled, you won't be seeing any serial data on Arduino IDE.
3. **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
