1. EMBEDDED SYSTEMS TUTORIAL8 - INTERFACING 16X2
ALPHANUMERIC LCD WITH AVR PART 1
Hi..!! friends this time I am here with a very very useful tutorial for embedded system beginners, this time
we are going to learn how to interface a LCD module, after learning LCD interfacing you will be able to
make so many important project related to LCD display….so lets start….!!
THING WE NEED TO START
For learning LCD interfacing we must have a 16X2 alphanumeric LCD display, of course our USBasp
programmer and ATmega 16.
For interfacing LCD we must have LCD library, u can found so many libraries on net but Mr. Peter
Fluery’s library is most trusted and most widely used one , THNX to him you can directly download his
library from this linklcd library
LCD PIN DISCRIPTION
A 16x2 alphanumeric LCD contains 16 pins and description of these pins is given below
1 VSS (GND )
2 VCC (+5V)
3 VEE ( adjust contrast)
4 RS
5 R/W
6 E
7 DB0
8 DB1
9 DB2
10 DB3
11 DB4
12 DB5

2. 13 DB6
14 DB7
15 LED+ (+5V)
16 LED- (GND)
In this tutorial we are using our LCD in 4bit mode so we will use DB4-DB7(PIN 11-14 of LCD) as DATA
pins.
USING LIBRARIES
The LCD library which u will download will contain mainly two files lcd.c and lcd.h, by changing the
PORT in lcd.h you can change the port of LCD connection, by default it is set to PORTA. You can also
change pins of LCD connection from same file for this purpose you have to open lcd.h with notepad , then
change PORT/PINS according to your choice and then save it. For adding library support in your
program you have to paste lcd.c and lcd.h in the same folder where your .c file of program is contained.
And these libraries can be added to the program by including these header file in starting of program#include”lcd.c”
#include”lc.h”
COMMANDS USED
In lcd.h file you can get information about the commands which we have to use in our program , I am
discussing some of them here but you can check the library to get knowledge about all the useful
command
Initializing the LCD
To initialize the LCD in program we have to this command is used
lcd_init(LCD_DISP_ON);
To move cursor at a specific position
lcd_gotoxy(x,y);
here x and y are the co-ordinates of desired location.
To clear the display
lcd_clrscr();
To set cursor to home position
lcd_home();
To display any text string
lcd_puts("desired text string");
in addition to these commands there are many more command but for starting interfacing these
commands are sufficient and we will discuss other commands later.
SAMPLE CODE

3. Here is a simple sample code to start with this time we are going to display a simple text on string on the
LCD .
#include <stdlib.h>
#include <avr/io.h>
#include <avr/pgmspace.h>
#include<util/delay.h>
#include "lcd.h"
#include "lcd.c"
int main(void)
{
while(1)
{
lcd_init(LCD_DISP_ON);
lcd_gotoxy(2,0);
lcd_puts("TECH_STRONG");
_delay_ms(500);
lcd_clrscr();
lcd_gotoxy(1,0);
lcd_puts("LCD INTERFACING");
lcd_gotoxy(2,1);
lcd_puts("BY ABHILASH");
_delay_ms(500);
lcd_clrscr();
}
}
CIRCUIT DIAGRAM FOR CONNECTIONS
So that’s it now just make a simple circuit as shown below.
// Initialize LCD
// setting cursor to (2,0)
// to display text
// wait for some time
// clear display
//setting cursor to (1,0)
// to display text
//setting cursor to (1,0)
// to display text
// wait for some time
// clear display

4. The contrast of LCD can be adjusted by using the variable resistance used here.
Now compile the program and burn your MCU with corresponding hex file and our first LCD interfacing
project is ready……now you can display any thing on the LCD …..yes I know you are going to display
your name first…..:p
I hope this article was useful for guys in case of any query, doubt or critical view just leave a comment. In
next LCD interfacing tutorial we will discuss about rotating a text , displaying integers and some basic
LCD projects……..till then bye….enjoy your LCD……!!