"Hello World!"

The LiquidCrystal library allows you to control LCD displays that are compatible with the Hitachi HD44780 driver. There are many of them out there, and you can usually tell them by the 16-pin interface.

This example sketch prints "Hello World!" to the LCD and shows the time in seconds since the Arduino was reset.

lcd photo

output of the sketch on a 16x2 LCD

The LCDs have a parallel interface, meaning that the microcontroller has to manipulate several interface pins at once to control the display. The interface consists of the following pins:

A register select (RS) pin that controls where in the LCD's memory you're writing data to. You can select either the data register, which holds what goes on the screen, or an instruction register, which is where the LCD's controller looks for instructions on what to do next.

A Read/Write (R/W) pin that selects reading mode or writing mode

An Enable pin that enables writing to the registers

8 data pins (D0 -D7). The states of these pins (high or low) are the bits that you're writing to a register when you write, or the values you're reading when you read.

There's also a display constrast pin (Vo), power supply pins (+5V and Gnd) and LED Backlight (Bklt+ and BKlt-) pins that you can use to power the LCD, control the display contrast, and turn on and off the LED backlight, respectively.

The process of controlling the display involves putting the data that form the image of what you want to display into the data registers, then putting instructions in the instruction register. The LiquidCrystal Library simplifies this for you so you don't need to know the low-level instructions.

The Hitachi-compatible LCDs can be controlled in two modes: 4-bit or 8-bit. The 4-bit mode requires seven I/O pins from the Arduino, while the 8-bit mode requires 11 pins. For displaying text on the screen, you can do most everything in 4-bit mode, so example shows how to control a 16x2 LCD in 4-bit mode.

Hardware Required

  • Arduino Board

  • LCD Screen (compatible with Hitachi HD44780 driver)

  • pin headers to solder to the LCD display pins

  • 10k ohm potentiometer

  • 220 ohm resistor

  • hook-up wires

  • breadboard


Before wiring the LCD screen to your Arduino board we suggest to solder a pin header strip to the 14 (or 16) pin count connector of the LCD screen, as you can see in the image above. To wire your LCD screen to your board, connect the following pins:

  • LCD RS pin to digital pin 12

  • LCD Enable pin to digital pin 11

  • LCD D4 pin to digital pin 5

  • LCD D5 pin to digital pin 4

  • LCD D6 pin to digital pin 3

  • LCD D7 pin to digital pin 2

  • LCD R/W pin to GND

  • LCD VSS pin to GND

  • LCD VCC pin to 5V

  • LCD LED+ to 5V through a 220 ohm resistor

  • LCD LED- to GND

Additionally, wire a 10k pot to +5V and GND, with it's wiper (output) to LCD screens VO pin (pin3).

click the images to enlarge

LCD Base bb Fritz

image developed using Fritzing. For more circuit examples, see the Fritzing project page


click the images to enlarge

LCD Base bb Schem

image developed using Fritzing. For more circuit examples, see the Fritzing project page


See Also

Last revision 2019/04/05 by SM