SegLCDLib
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Getting Started with SegLCDLib

Requirements

  • Arduino IDE: Version 1.8.13 or later
  • Hardware: Arduino-compatible microcontroller (AVR, ARM, ESP32, etc.)
  • Wire Library: Built-in; used for I2C controllers (included with Arduino IDE)
  • Display Module: One of the supported LCD displays

Installation

Option 1: Arduino Library Manager (Recommended)

  1. Open Arduino IDE
  2. Go to Sketch → Include Library → Manage Libraries...
  3. Search for SegLCDLib
  4. Click Install

Option 2: Manual Installation

  1. Download or clone: https://github.com/petrkr/SegLCDLib
  2. Copy the SegLCDLib folder to your Arduino libraries folder:
    • Windows: Documents\Arduino\libraries
    • macOS: ~/Documents/Arduino/libraries
    • Linux: ~/Arduino/libraries
  3. Restart Arduino IDE

First Project: 4-Digit Display with Degree Symbol (HT1621)

This example uses the 4-digit LCD with degree symbol (integrated HT1621 controller). This is a ready-made module commonly found on AliExpress, no soldering needed.

Wiring

Connect 3 GPIO pins and power to your Arduino:

Module Pin Arduino Pin
CLK Pin 5
DATA Pin 6
CS Pin 7
VCC 3.3V
GND GND

Note: Adjust pins 5, 6, 7 if they conflict with other components.

Code

#include "SegLCD_HT1621_4SegDegree.h"
// Create LCD instance (pins: CLK, DATA, CS)
SegLCD_HT1621_4SegDegree lcd(5, 6, 7);
void setup() {
lcd.init(); // Initialize display
}
void loop() {
int temp = 23; // Temperature in Celsius
lcd.setCursor(0, 0); // Move to first digit
lcd.print(temp); // Print 23 on display
lcd.showDegree(); // Show degree symbol (°)
delay(1000);
}
SegLCD_HT1621_4SegDegree.h
HT1621 driver for 4-digit LCD with degree symbol and colon.
SegLCD_HT1621_4SegDegree
4-digit 7-segment LCD with degree symbol and colon (HT1621).
Definition SegLCD_HT1621_4SegDegree.h:19

Running

  1. Select your board: Tools → Board → Choose your Arduino
  2. Select COM port: Tools → Port
  3. Upload: Sketch → Upload (Ctrl+U)
  4. Display should show "23°" with degree symbol

Choosing Your LCD Display

Use this table to find the right display for your project:

Your Need Controller LCD Module Wiring
Simplest PCF85176 RAW LCD I2C only
Show digits PCF85176 6-digit with battery/signal I2C, 4 pins
Temperature PCF85176 Temp/Humidity I2C, 4 pins
Small display HT1621 4-digit with degree 3 pins
Many digits HT1621 6-digit with battery 3 pins
16-segment HT1622 10-digit 16-segment 3 pins
Advanced VK0192 5-digit with battery 3 pins

For detailed specifications and purchase links, see Supported LCDs.

Basic API Reference

Display Control

lcd.init(); // Initialize display and clear
lcd.clear(); // Turn off all segments
lcd.on(); // Turn display on
lcd.off(); // Turn display off
lcd.home(); // Set cursor to 0,0

Positioning and Output

lcd.setCursor(row, col); // Move cursor to row/column
lcd.print(value); // Output number or string
lcd.write(byte); // Output single character/segment byte

Features (display-dependent)

lcd.setBattery(level); // Set battery indicator (0-3)
lcd.setSignal(bars); // Set signal strength (0-4)
lcd.showDegree(); // Show degree symbol

See Architecture for class hierarchy and full API Reference for complete method documentation.

Common Issues

Display not showing:

  • Verify I2C address: Use example sketch PCF85176/RawLCD to scan addresses
  • Check wiring: SDA, SCL, VCC, GND connections
  • Confirm board selection and COM port in Arduino IDE

Wrong I2C address:

  • PCF85176 I2C address is set by SA0 pin: 0x38 (SA0=0) or 0x39 (SA0=1)
  • A0-A2 are subaddresses in the protocol, not I2C address pins
  • HT1621/HT1622/VK0192 use 3-wire serial (no I2C address)

Library not found:

  • Restart Arduino IDE after installation
  • Verify installation path: Check Arduino/libraries/SegLCDLib/ exists

Next Steps

Resources