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How to Interface 4 Bit LCD with Arduino


Developed By: 
Ajish Alfred
Liquid Crystal Display is made use in various kinds of devices from small display screen in calculator to large screens in televisions. There are lots of advantages in using the LCD displays in systems like power efficiency, thin size, low cost etc. LCD based small display modules are normally found in all kinds of embedded devices.The LCD even though looks simple, but it is actually difficult to make it work.
The LCD works with voltage pulses only and that with precise timing and voltage levels. Hence special kinds of LCD drivers are developed to drive the LCD. Two or more of this kind of driver ICs together with the LCD screen forms LCD modules which are normally found in embedded systems.The LCD module makes a system stand-alone which can take input and display the corresponding output. This particular project demonstrates how to interface a 16x2 LCD display with an Arduino board.


How To Interface 4 Bit LCD With Arduino



Any AVR microcontroller based board which follows the standard Arduino schematic and is flashed with the Arduino bootloader can be called an Arduino board. There is no other tool available which helps in easy prototyping like the Arduino does.  The Arduino board has all the required circuitary to get the built-in AVR microcontroller running. When it comes to programming the Arduino board anyone who have basic knowledge of c programming can quickly get started with the Arduino IDE. The tutorial on Getting started with Arduino explains about the steps required to get start with an Arduino board. The Arduino board used in this project is the Arduino pro-mini board and the IDE version of the Arduino is 1.0.3 for windows. The image of the Arduino pro-mini board and the Arduino IDE are shown below;




Since the Arduino pro-mini board has no circuitary for interfacing it with the serial port or the USB port of the PC, an external USB to TTL converter board is required to connect it with the PC. This hardware helps in programming the Arduino board and also helps in the serial communication with the USB port of the PC.


It is assumed that the reader has gone through the project how to get started with the Arduino and tried out all the things discussed there. The Arduino IDE has so many functions which help one to interface the four bit LCD module. There are functions to initialize the LCD module and to write character characters in the LCD module. The functions used in the coding of this projects are lcd.begin(), and lcd.print(). The functions are available in the library <LiquidCrystal.h> and one should initialize the library before using those functions.


This function should be called to initialize the four bit LCD library and then only the library functions can be called in the code. The function has six parameters which should be provided during a function call as per the circuit connection with the Arduino board and the LCD module. The details of the function parameters are listed in the order below.


For example the following statement can be used to initialize an LCD library for the code written for the circuit in which the RS pin is connected to pin12, Enable pin to 11, and D4, D5, D6 and D7 to pins 5, 4, 3 and 2 resepectievely.


This function can be used to initialize the LCD module. The first parameter is the number of rows of the LCD module in use and the second parameter is the number of columns. The lcd.begin() function can be used to initialize a 16*2 LCD using the statement;

lcd.begin(16, 2);

The above statement will initialize the 16*2 LCD in four bit mode with two line display mode.


This function is used to display an ASCII character or string in an LCD screen. If a value is provided as the parameter of the function, it will format that value into displayable string and then display it on the LCD.

The lcd.print() function is analogues to the function Serial.print() discussed with the project on how to do serial debugging with Arduino, how to do serial input and output with Arduino and how send serial data from Arduino.

The lcd.print() function can be used to print a string using the statement as shown below;

lcd.print("hello world");

The above statement will print the string “hello world” in the LCD screen. If the value of a variable need to be printed on the LCD screen the same function can be used as it can format a value to the ASCII string representing the value.


In the above statement the value 100 is formatted to string “100” by the lcd.print() function and then displays it on the LCD module.


The code first includes the <LiquidCrystal.h> library which has all the function required to access the LCD module. The 16*2 LCD module used in this project is initialized using the function lcd.begin(). The function lcd.print() is then used to print data on the LCD module.

// include the library code:

#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins

LiquidCrystallcd(12, 11, 5, 4, 3, 2);

// give the LED pin a name:

int led = 6;

void setup()


  // set up the LCD's number of columns and rows:

lcd.begin(16, 2);

  // Print a message to the LCD.

lcd.print("ENGINEERS GARAGE");

  // initialize the digital pin as an output.

pinMode(led, OUTPUT);  


void loop()


digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)

delay(1000);               // wait for a second

digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW

delay(1000);               // wait for a second


The code initializes the module, display a string in the module using the functions available in the <LiquidCrystal.h> library. The code the blinks an LED in an infinite loop using the pinMode () and digitalWrite () functions discussed in the project on how to get started with the Arduino and how to use digital input and output of Arduino.

Circuit Diagram



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