LiquidCrystal_PCF8574

Arduino Library for LiquidCrystal displays with I2C PCF8574 adapter

A library for driving LiquidCrystal displays (LCD) by using the I2C bus and an PCF8574 I2C adapter.

There are modules that can be soldered or stacked to the display that offers an I2C interface for communication instead of the 8+ digital lines that are used to send data to the display.

Most of these modules use the wiring that is supported by this library’s default configuration. If you use a module with a different wiring, you can use one of the class constructors which allow you to specify the pin assignments.

See the web site for more details and pictures: https://www.mathertel.de/Arduino/LiquidCrystal_PCF8574.aspx

Example

The initialization of an LCD display attached to a I2C bus differs from the standard LiquidCrystal library, but the functions for sending text to the display are the same.

Here is a minimal example showing how to display “Hello World” on an LCD using the default I2C Wire interface:

LiquidCrystal_PCF8574 lcd(0x27);  // Create LCD at default I2C address
lcd.begin(16, 2, Wire);           // Initialize 16x2 display

// now start using it
lcd.setCursor(0, 0);
lcd.print("Hello World");

Version 2.3.0 (2026-02-22)

• adding the function isConnected() to check if the LCD display is connected and responsive via I2C.
• Documentation

Version 2.2.0 (2023-04-03)

The default i2c address 0x27 is set as default parameter.

You can use an explicit i2c address with

LiquidCrystal_PCF8574 lcd(0x22);  // set the LCD address to 0x22

or you can rely on the default i2c address = 0x27 with

LiquidCrystal_PCF8574 lcd();  // use the default LCD address == 0x27

See datasheet of PCF8574 (and PCF8574A) for further info on usable i2c addresses.

Thanks for contribution from @robaol

Version 2.1.0 (2022-08-21)

Enables using a non-default i2c / TwoWire port for boards that support multiple ports.

Added example LCD_Burnin.ino showing how to transfer a 20 char and 4 lines buffer to a device all at once.

Thanks for additions from @uutzinger

Changes Version 2.0.0 (2022-05-26)

• The interface was modified to use 8-bit datatypes as supported by the underling hardware.
• A createChar version with PROGMEM character data for AVR processors was added.
• A constructor with pin assignments was added to allow easy adoption to other wirings than the default.

Thanks for additions from @markisch.