LCD interfacing with ATMEGA32 AVR MICROCONTROLLER

INTERFACING OF LCD WITH ATMEGA32 AVR MICROCONTROLLER.In this article you will learn what LCD is and how to interface LCD with AVR microcontroller Atmega32 using 8-bit mode. What is the basic difference between 8-bit mode and 4-bit mode? How to write code for LCD interfacing in C language and what are the basic commands used for LCD programming. Here we will also learn how to program LCD and sends command/ data to LCD.




LCD stands for Liquid Crystal Display, is an electronic device which is used for data display. LCDs are preferable over seven segments and LEDs as they can easily represent data in form of alphabets, characters, numbers or animations. LCDs are very easy to program and make your work quite attractive and simple. Numerous types of LCDs are available in market such as 16X2, 16X4, 20X2, 20X4, graphical LCDs (128X64) etc. The LCD which we are using is 16X2 alphanumeric LCD, it display 32 characters in two rows means in one row we have 16 characters.

PIN DESCRIPTION OF LCD

16X2 LCD can interface with AVR microcontroller by using two modes, 4-bit mode or 8-bit mode. In this article we will use 8-bit mode for interfacing. In 8-bit mode we send command to LCD by using eight data lines (D0-D7) while in 4-bit mode we use four data lines (D5-D7) for sending command and data. These data lines can be connected to any port of Atmega32.

 

PIN NO.PIN NAMEDESCRIPTION
1VCCSupply pin (+5V DC)
2VDDGround pin
3VEEContrast pin
4RSRegister selection pin (either data or command)RS=0: Command Register ,

RS=1: Data Register

5RWSelects Read or Write operationRW=0: for write

RW=1:  for read




6EEnable pin
7D0Data pin 0
8D1Data pin 1
9D2Data pin 2
10D3Data pin 3
11D4Data pin 4
12D5Data pin 5
13D6Data pin 6
14D7Data pin 7

 

HOW TO PROGRAM LCD?

Basically there are two registers, command and data. When we are giving command to LCD, we select command register and when we are sending data to LCD for display, we select data register. Command is an instruction given to LCD in order to perform required function according to the given command. In order to display textual information, data is send to LCD.

SENDING COMMANDS ON LCD

For sending commands on LCD we have to write command on data pins. For this, selects:

RS = 0 >> selects command register

RW = 0 >> selects write operation

E >> make enable pin from high to low

SENDING DATA ON LCD

For sending data on LCD we have to write data on data pins. For this, selects:

RS = 1 >> selects data register

RW = 0 >> selects write operation

E >> make enable pin from high to low

SCHEMATIC

We design our circuit on proteus. Circuit diagram is given below:

LCD interfacing with ATMEGA32 AVR MICROCONTROLLER

LCD interfacing with ATMEGA32 AVR MICROCONTROLLER

CODE FOR INTERFACING LCD

We use Atmel studio 6 for development of code and the code is written in C language.

#ifndef F_CPU

# define F_CPU 16000000UL // clock speed is 16MHz

#endif

 

#include<avr/io.h>        // AVR header

#include<util/delay.h>    // delay header

 

//******************LCD PROGRAM STARTS*********************//

#define LCD_DATA PORTB          // port B is selected as LCD data port

#define ctrl PORTD              //  port D is selected as LCD command port

#define en PD7                  // enable signal is connected to port D pin 7

#define rw PD6                  // read/write signal is connected to port D pin 6

#define rs PD5                  // register select signal is connected to port D pin 5

 

void LCD_cmd(unsigned char cmd);

void init_LCD(void);

void LCD_write(unsigned char data);

 

int main(void)

{

DDRB=0xFF;              // set LCD data port as output

DDRD=0xE0;              // set LCD signals (RS, RW, E) as out put

init_LCD();             // initialize LCD

_delay_ms(100);         // delay of 100 Milli seconds

 

LCD_cmd(0x0C);          // display on, cursor off

_delay_ms(100);

 

LCD_write(‘ ‘);         // call a function to display space on LCD

_delay_ms(1);

LCD_write(‘ ‘);         // call a function to display space on LCD

_delay_ms(1);

LCD_write(‘ ‘);         // call a function to display space on LCD

_delay_ms(1);

LCD_write(‘ ‘);         // call a function to display space on LCD

_delay_ms(1);

LCD_write(‘ ‘);         // call a function to display space on LCD

_delay_ms(1);

LCD_write(‘A’);         // call a function to display “A” on LCD

_delay_ms(100);

LCD_write(‘V’);         // call a function to display “V” on LCD

_delay_ms(100);

LCD_write(‘R’);         // call a function to display “R” on LCD

_delay_ms(100);

 

LCD_cmd(0xC0);          // move cursor to the start of 2nd line

_delay_ms(100);

 

LCD_cmd(0x0C);          // display on, cursor off

_delay_ms(100);

 

LCD_write(‘ ‘);         // call a function to display space on LCD

_delay_ms(1);

LCD_write(‘ ‘);

_delay_ms(1);

LCD_write(‘ ‘);

_delay_ms(1);

LCD_write(‘A’);        // call a function to display “A” on LCD

_delay_ms(100);

LCD_write(‘t’);        // call a function to display “t” on LCD

_delay_ms(100);

LCD_write(‘m’);        // call a function to display “m” on LCD

_delay_ms(100);

LCD_write(‘e’);        // call a function to display “e” on LCD

_delay_ms(100);

LCD_write(‘g’);        // call a function to display “g” on LCD

_delay_ms(100);

LCD_write(‘a’);        // call a function to display “a” on LCD

_delay_ms(100);

LCD_write(‘3’);        // call a function to display “3” on LCD

_delay_ms(100);

LCD_write(‘2’);        // call a function to display “2” on LCD

_delay_ms(100);

LCD_cmd(0x0E);          // make display ON, cursor ON

_delay_ms(1);

 

return 0;

}

void init_LCD(void)

{

LCD_cmd(0x38);           // initialization in 8bit mode of 16X2 LCD

_delay_ms(1);

LCD_cmd(0x01);          // make clear LCD

_delay_ms(1);

LCD_cmd(0x02);          // return home

_delay_ms(1);

LCD_cmd(0x06);          // make increment in cursor

_delay_ms(1);

LCD_cmd(0x80);          // “8” go to first line and “0” is for 0th position

_delay_ms(1);

 

return;

}

 

//**************sending command on LCD***************//

void LCD_cmd(unsigned char cmd)

{

LCD_DATA = cmd;      // data lines are set to send command

PORTD  &= ~(1<<rs);  // RS sets 0

PORTD  &= ~(1<<rw);  // RW sets 0

PORTD  |= (1<<en);   // make enable from high to low

_delay_ms(100);

PORTD  &= ~(1<<en);

 

return;

}

 

//*****************write data on LCD*****************//

void LCD_write(unsigned char data)

{

LCD_DATA= data;       // data lines are set to send command

PORTD  |= (1<<rs);    // RS sets 1

PORTD  &= ~(1<<rw);   // RW sets 0

PORTD  |= (1<<en);    // make enable from high to low

_delay_ms(100);

PORTD &= ~(1<<en);

 

return ;

}

 

SIMULATION ON PROTEUS

Compile the above code and dump the HEX file in AVR microcontroller as described in the previous tutorials. Make necessary settings and check the display on LCD.

LCD interfacing with ATMEGA32

LCD interfacing with ATMEGA32

BASIC COMMANDS USED IN LCD DISPLAY

COMMANDSDESCRIPTION
0x01Clear screen
0x02return home
0x04Cursor decrement
0x05Display shifts to right
0x06Cursor increment
0x07Display shifts to left
0x08Cursor and display OFF
0x10Cursor position Shifts to left
0x14Cursor position shifts to right
0x38Using two lines, 8-bit mode
0x28Using two lines, 4-bit mode
0x80Move cursor to the beginning of first line
0x0CDisplay ON, cursor OFF
0XC0Move cursor to the beginning of second line
0x0ADisplay OFF, cursor ON
0x0EDisplay ON, cursor blinking
0x30For display in one line in 8-bit mode
0x20For display in one line in 4-bit mode
0x0FDisplay data on cursor blinking
0x18Shift complete data to left side
0x1CShift complete data to right side

 

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One Response

  1. M Zeeshan (Air university,Islamabad) March 8, 2017

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