All displays use segment LCD technology controlled by I2C or 3-wire serial protocol. Select by controller type and application.

PCF85176 (I2C) Displays

RAW LCD

Purpose: Testing and debugging new LCD implementations

Type: Test harness
Wiring: I2C only (2 pins: SDA, SCL)
Features: Send raw segment data directly to controller
Use Case: Prototype new displays before creating dedicated driver
Example: examples/PCF85176/RawLCD/

6-Digit Signal/Battery/Progress

Specifications:

Digits: 6 7-segment digits
Features: Signal strength (4 bars), Battery level (3 states), Progress indicator
Wiring: I2C (SDA, SCL)
I2C Address: 0x38 (SA0=0) or 0x39 (SA0=1)
Controller: PCF85176
Image:
Example: examples/PCF85176/6DigSigBattProgress/
Purchase: https://aliexpress.com/item/1005009214559485.html

Code Example:

#include "SegLCD_PCF85176_6DigSigBattProgress.h"
SegLCD_PCF85176_6DigSigBattProgress lcd(Wire);
 
lcd.init();
lcd.setCursor(0, 0);
lcd.print(123456);
lcd.setSignal(3);   // 3 of 4 bars
lcd.setBattery(2);  // Medium battery

2-Row 4-Digit Signal/Battery/Power

Specifications:

Digits: 2 rows × 4 digits
Features: Signal (1 bit), Battery (4 levels), Power icon
Wiring: I2C (SDA, SCL)
I2C Address: 0x38 (SA0=0) or 0x39 (SA0=1)
Controller: PCF85176
Image:
Example: examples/PCF85176/2Row4DigSigBatPwr/

Code Example:

#include "SegLCD_PCF85176_2Row4DigSigBatPwr.h"
SegLCD_PCF85176_2Row4DigSigBatPwr lcd(Wire);
 
lcd.init();
lcd.setCursor(0, 0);
lcd.print(1234);
lcd.setCursor(1, 0);
lcd.print(5678);
lcd.setSignalLevel(1);
lcd.setBatteryLevel(4);
lcd.setPowerSymbol(true);

One Digit (Up to 5 Segments)

Specifications:

Digits: 1 custom segment display
Features: Customizable segment layout (up to 5 segments)
Wiring: I2C (SDA, SCL)
I2C Address: 0x38 (SA0=0) or 0x39 (SA0=1)
Controller: PCF85176
Image:
Example: examples/PCF85176/OneDigit/
Purchase: https://aliexpress.com/item/1005005410565386.html

Temperature/Humidity

Specifications:

Digits: 6 7-segment digits
Features: Temperature and humidity symbols
Wiring: I2C (SDA, SCL)
I2C Address: 0x38 (SA0=0) or 0x39 (SA0=1)
Controller: PCF85176
Image:
Example: examples/PCF85176/TempHumidity/
Purchase: https://aliexpress.com/item/1005003044283980.html

Code Example:

#include "SegLCD_PCF85176_TempHum.h"
SegLCD_PCF85176_TempHum lcd(Wire);
 
lcd.init();
lcd.setCursor(0, 0);  // Temperature row
lcd.print(23);        // 23°C
lcd.setCursor(1, 0);  // Humidity row
lcd.print(45);        // 45%

T1T2 LCD

Specifications:

Layout: 3-row display (Clock, T1 Label, T2 Label)
Features: Multi-zone control for temperature sensors
Wiring: I2C (SDA, SCL)
I2C Address: 0x38 (SA0=0) or 0x39 (SA0=1)
Controller: PCF85176
Image:
Example: examples/PCF85176/T1T2Lcd/

4DR821B / 4DT821B (Tesla)

Specifications:

Segments: Custom Tesla dashboard display
Features: Multiple symbol zones
Wiring: I2C (SDA, SCL)
I2C Address: 0x38 (SA0=0) or 0x39 (SA0=1)
Controller: PCF85176
Image:
Reference: https://www.teslakatalog.cz/4DR821B.html
Example: examples/PCF85176/4DR821B/

4+6 Digit Maint/Bat/Sig/Units

Specifications:

Digits: 4 digits (main) + 6 digits (status)
Features: Maintenance, Battery, Signal, Unit symbols
Wiring: I2C (SDA, SCL)
Controller: PCF8576 (enhanced variant)
Image:
Example: examples/PCF8576/4Seg6SegMaintSegBatUnits/
Purchase: https://aliexpress.com/item/1005009599538480.html

HT1621 (3-Wire Serial) Displays

4-Digit with Degree Symbols

Specifications:

Digits: 4 7-segment digits
Features: Degree symbol, Colon for time display
Wiring: 3 pins (CLK, DATA, CS) + Power + GND
Protocol: 3-wire serial
Controller: HT1621 (integrated in module)
Image:
Example: examples/HT1621/4DigDeg/
Purchase: https://aliexpress.com/item/1005009301473702.html

Code Example:

#include "SegLCD_HT1621_4SegDegree.h"
 
// Pin configuration
const int CLK = 5, DATA = 6, CS = 7;
SegLCD_HT1621_4SegDegree lcd(CLK, DATA, CS);
 
lcd.init();
lcd.setCursor(0, 0);
lcd.print(25);      // Display "25°"

Wiring Example (Arduino Uno):

HT1621 Module  →  Arduino
CLK            →  Pin 5
DATA           →  Pin 6
CS (chip sel)  →  Pin 7
VCC            →  3.3V or 5V
GND            →  GND

6-Digit with Battery

Specifications:

Digits: 6 7-segment digits
Features: Battery level indicator (3-4 states)
Wiring: 3 pins (CLK, DATA, CS) + Power + GND
Protocol: 3-wire serial
Controller: HT1621 (integrated)
Image:
Example: examples/HT1621/6DigBat/
Purchase: https://aliexpress.com/item/1005005555160141.html

Code Example:

#include "SegLCD_HT1621_6SegBat.h"
 
const int CLK = 5, DATA = 6, CS = 7;
SegLCD_HT1621_6SegBat lcd(CLK, DATA, CS);
 
lcd.init();
lcd.print(123456);
lcd.setBattery(2);  // Medium battery

LCM0844

Specifications:

Digits: 8 7-segment digits
Features: Left/right units, status labels, battery/load indicators, power-flow symbols
Wiring: 3 pins (CLK, DATA, CS) + Power + GND
Protocol: 3-wire serial
Controller: HT1621 (integrated)
Image:
Example: examples/HT1621/LCM0844/
Purchase: https://www.aliexpress.com/item/1005010575036798.html

Code Example:

#include "SegLCD_HT1621_LCM0844.h"
 
const int CLK = 5, DATA = 6, CS = 7;
SegLCD_HT1621_LCM0844 lcd(CLK, DATA, CS);
 
lcd.init();
lcd.print("12.34");
lcd.setBatteryLevel(4);
lcd.setLoadLevel(3);

LCM88128

Specifications:

Digits: 8 7-segment digits
Features: Left/right units, status labels, battery/load/PV indicators, power-flow symbols
Wiring: 3 pins (CLK, DATA, CS) + Power + GND
Protocol: 3-wire serial
Controller: HT1621 (integrated)
Image:
Example: examples/HT1621/LCM88128/
Purchase: https://www.aliexpress.com/item/1005010569015863.html

Code Example:

#include "SegLCD_HT1621_LCM88128.h"
 
const int CLK = 5, DATA = 6, CS = 7;
SegLCD_HT1621_LCM88128 lcd(CLK, DATA, CS);
 
lcd.init();
lcd.print("12.34");
lcd.setPVLevel(4);
lcd.setBatteryLevel(3);
lcd.setLoadLevel(2);
lcd.setUnits(SegLCD_HT1621_LCM88128::UNIT_RIGHT_VOLT);
lcd.setSymbols(SegLCD_HT1621_LCM88128::SYMBOL_LINE_WIND_TO_ACDC);

LCM59011

Specifications:

Digits: 4 7-segment digits
Features: Colon, wifi signal, battery indicator, MCB label, units, status symbols
Wiring: 3 pins (CLK, DATA, CS) + Power + GND
Protocol: 3-wire serial
Controller: HT1621 (integrated)
Image:
Example: examples/HT1621/LCM59011/

Code Example:

#include "SegLCD_HT1621_LCM59011.h"
 
const int CLK = 5, DATA = 6, CS = 7;
SegLCD_HT1621_LCM59011 lcd(CLK, DATA, CS);
 
lcd.init();
lcd.print("12:3");
lcd.setSignalLevel(4);
lcd.setBatteryLevel(5);
lcd.setLabels(SegLCD_HT1621_LCM59011::LABEL_MCB);
lcd.setUnits(SegLCD_HT1621_LCM59011::UNIT_PERCENT);
lcd.setSymbols(SegLCD_HT1621_LCM59011::SYMBOL_ECO | SegLCD_HT1621_LCM59011::SYMBOL_BLUETOOTH);

RAW LCD (HT1621)

Purpose: Testing and prototyping with HT1621

Type: Test harness
Wiring: 3-wire serial (CLK, DATA, CS)
Features: Send raw segment data to HT1621
Example: examples/HT1621/RawLCD/

HT1622 (3-Wire Serial, Enhanced)

10-Digit 16-Segment Display

Specifications:

Digits: 10 digits with 16-segment layout
Features: Enhanced segment capability (alphanumeric capable)
Wiring: 3 pins (CLK, DATA, CS) + Power + GND
Protocol: 3-wire serial (4μs timing)
Controller: HT1622 (integrated, larger RAM)
Image:
Example: examples/HT1622/10Digit16SegmentLCD/
Purchase: https://aliexpress.com/item/1005003062619251.html

RAW LCD (HT1622)

Purpose: Testing and prototyping with HT1622

Type: Test harness
Wiring: 3-wire serial (CLK, DATA, CS)
Features: Send raw segment data to HT1622
Timing: Requires 4μs pulse width
Example: examples/HT1622/RawLCD/

VK0192 (3-Wire Serial)

5-Digit Signal/Battery/Progress

Specifications:

Digits: 5 7-segment digits
Features: Signal bars (4), Battery level (3), Progress indicator
Wiring: 3 pins (CLK, DATA, CS) + Power + GND
Protocol: 3-wire serial (4μs timing)
Controller: VK0192 (24×8 bit RAM, irregular addressing)
Image:
Example: examples/VK0192/5DigSigBattProgress/
Purchase: https://aliexpress.com/item/1005009000021475.html

Code Example:

#include "SegLCD_VK0192_5SegSigBatProg.h"
 
const int CLK = 5, DATA = 6, CS = 7;
SegLCD_VK0192_5SegSigBatProg lcd(CLK, DATA, CS);
 
lcd.init();
lcd.print(12345);
lcd.setSignal(3);    // 3 of 4 bars
lcd.setBattery(1);   // Low battery

Quick Comparison

Controller	Protocol	Pins	I2C Addr	Examples	Complexity
PCF85176	I2C	2	0x38/0x39	7	Simple
PCF8576	I2C	2	0x38/0x39	1	Simple
HT1621	3-wire	3	N/A	4	Medium
HT1622	3-wire	3	N/A	2	Medium
VK0192	3-wire	3	N/A	1	Advanced

Adding a New Display

Don't see your LCD? Follow the Adding New LCD guide to create support for any segment display.

Resources

Getting Started: Getting Started Guide
Architecture: Library Architecture
Controller Details: Controllers
Creating Drivers: Adding New LCD
API Reference: Full API Documentation