Interfacing LCD with the ATmega32

Components Required

• ATmega32 microcontroller
• AVR Programmer Board
• Crystal
• Capacitors
• 16x2 LCD
• +5V supply
• Breadboard
• Connecting Wires

Circuit Diagram

Description

DB0-DB7: Data Pins( use DB4-DB7 in 4 bit mode) 


RS(Register Select) : 1 - Data is sent , 0 - Command is sent . 


R/W(Read/Write) :1 - Read the LCD , 0 - Write to LCD. 


E(Enable): to enable an operation . first make low(0) to send data and then set the other two control lines and when they are configured, bring E high (1) and wait for the minimum amount of time required by the LCD and bring it low (0) again. 


VEE: Contrast Adjust Pin.



Connections 

• PC0 to PC7 are connected to the data pins D0 to D7 of the LCD.
• VDD and VEE are connected to the +5 volts directly.
• VEE can be connected to a potentiometer to adjust the contrast.
• VSS is connected to ground.
• RS, RW and E are connected to PD5, PD6 and PD7 respectively.
• A crystal is connected to XTAL1 and XTAL2 pins to provide the clock pulse.
• Reset is connected to +5V.

Source Code

/*

The following code will display the string defined in the main function.

 */ 

#include <avr/io.h>

#include <util/delay.h>

#ifndef F_CPU

#define F_CPU 1000000UL //Frequency of the external crystal

#endif

/*CWR - Command Word Register*/

#define ENABLE_LCD PORTD |= 0x80 //CWR state  to enable LCD

#define DISABLE_LCD PORTD &= ~0x80//CWR state to disable LCD

#define SET_LCD_DATA PORTD |= 0x20 //CWR state to send data

#define SET_LCD_CMD PORTD &= ~0x20 //CWR state to send command

void LCD_WriteCommand (unsigned char CMD);

void LCD_WriteData (unsigned char Data);

void LCD_DisplayString_F(char row, char column,char *string);

void LCD_Cursor(char row, char column);

void init_devices(void)

{

DDRC = 0xFF; //All pins of PORTC declared as Output

PORTC = 0x00;//Initially all pins declared as output low

DDRD = 0xF0;//Pins D4 to D7 declared as input,remaining as o/p

PORTD = 0x00;//All output pins as low

_delay_ms(100); // wait for 100ms

LCD_WriteCommand (0x38); // 8 data lines

LCD_WriteCommand (0x06); // cursor setting

LCD_WriteCommand (0x0f); // display ON

LCD_WriteCommand (0x01); // clear LCD memory

_delay_ms (10); // 10ms delay after clearing LCD

}

int main(void)

{

init_devices();

        //Text to be displayed in first row

LCD_DisplayString_F(1,1,"    ROBOWARES ");

        //Text to be displayed in second row

LCD_DisplayString_F(2,1,"rickruling.blogspot.in");

return 0;

} 

void LCD_WriteCommand (unsigned char Command)

{

SET_LCD_CMD; // Set LCD in command mode

PORTC = Command; // Load data to port

ENABLE_LCD; // Write data to LCD

_delay_ms(1);

DISABLE_LCD; // Disable LCD

_delay_ms(1); // wait for 1ms

}

void LCD_WriteData (unsigned char Data)

{

SET_LCD_DATA; // Set LCD in data mode

PORTC = Data; // Load data to port

ENABLE_LCD; // Write data to LCD

_delay_ms(1);

DISABLE_LCD; // Disable LCD

_delay_ms(1); // wait for 1ms

}

void LCD_DisplayString_F (char row, char column ,char *string)

{

         /*Break the string into characters and send them for the display*/

LCD_Cursor (row, column);

while (*string)//Loop till the string is not null

LCD_WriteData(*string++);

}

void LCD_Cursor (char row, char column)

{

switch (row)

{

case 1:     //Set the position in the first row

                 LCD_WriteCommand (0x80 + column - 1);

break;

case 2:     //Set the position in the second row

                 LCD_WriteCommand (0xC0 + column - 1);

break;

default: break;

}

}

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