problem interfacing 16x2 lcd (in 4 bit mode) with ATMEGA 32

[yviswanathbe]

Hi Friends,

I am facing problem with interfacing lcd in 4 bit mode with atmega32 micro controller.

I have done in 8 bit mode.

for initial testing i am just sending a string to LCD, but nothing is visible in the LCD. LCD is blank.

and the same lcd is working fine in 8 bit mode.

I am not able to trace the problem.

i have attached my source code. Some body please help me in solving the issue.

#include <mega32.h>
#include <stdio.h>
#include <delay.h>

#define LCDPORT     PORTD
#define RS          PORTB.0
#define RW          PORTB.1
#define E           PORTB.2
#define led         PORTB.3
#define flag        PIND.7

void lcd_init_write(unsigned char);
void lcd_com(unsigned char);
void lcd_data(unsigned char);
void lcd_init(void);
void lcd_puts(char *);
void busy();

void lcd_init_write(unsigned char a)
{
          //busy();
          RS=0;
          RW=0;
          LCDPORT=a;
          E=1;
          delay_ms(2);
          E=0;
}
void busy()
{
          PORTD=0x00;
          DDRD=0x00;
          RS=0;
          RW=1;
          while(flag!=0)
          {
                    E=0;
                    delay_ms(2);
                    E=1;
          }
          PORTD=0xFF;
          DDRD=0xFF;
}


void lcd_com(unsigned char a)
{
          unsigned char temp; 
          busy();                                               
          RS=0;
          RW=0; 
          temp=a; 
          temp=temp & 0xF0;
          //LCDPORT=LCDPORT & 0xF0; 
          LCDPORT=LCDPORT & temp;                          
          E=1;
          delay_ms(2);                    
          E=0;
          temp=a;
          temp=temp<<4;
          temp=temp & 0xF0;
          temp=temp>>4; 
          //LCDPORT=LCDPORT | 0xF0;                                                                                 
          LCDPORT=LCDPORT & temp;
          LCDPORT=LCDPORT & 0x0F;                              
          E=1;
          delay_ms(2);                   
          E=0;
}

void lcd_data(unsigned char a)
{
         unsigned char temp; 
          busy();                                               
          RS=1;
          RW=0; 
          temp=a; 
          temp=temp & 0xF0;
          //LCDPORT=LCDPORT & 0xF0; 
          LCDPORT=LCDPORT & temp;                          
          E=1;
          delay_ms(2);                    
          E=0;
          temp=a;
          temp=temp<<4;
          temp=temp & 0xF0;
          temp=temp>>4; 
          //LCDPORT=LCDPORT | 0xF0;                                                                                 
          LCDPORT=LCDPORT & temp;
          LCDPORT=LCDPORT & 0x0F;                              
          E=1;
          delay_ms(2);                   
          E=0;
}
void lcd_init(void)
{
          lcd_init_write(0x30); 
          delay_ms(5);  
          lcd_init_write(0x30); 
          delay_ms(1);  
          lcd_init_write(0x30);   
          lcd_init_write(0x20);   
          lcd_com(0x28);         
          lcd_com(0x06);          
          lcd_com(0x08);             
          lcd_com(0x01);          
          lcd_com(0x0F);
          lcd_com(0x02);
}
void lcd_puts(char *str)
{
          while(*str)
          lcd_data(*str++);
}

void main()
{
          DDRB=0x0F;
          PORTB=0x00;
          DDRD=0xFF;
          PORTD=0xFF;  
          delay_ms(20);
          lcd_init();                   //Intilize LCD in 4-Bit Mode
          lcd_com(0x80);                // Start Cursor From First Line 
          lcd_puts("Hello");          //Print HELLO on LCD
          //lcd_com(0x01);
          //lcd_com(0xC0);              // Start Cursor From Second Line
          //lcd_puts("World");          //Print HELLO on LCD
          while(1);                     //Stay Forever Here
}

Thanks and Regards,
Viswanath.

 

[d@nny]

which 4 bit pins you are using
attached your schematic please

 

[nandhu015]

temp=temp<<4;
temp=temp & 0xF0;
temp=temp>>4;
//LCDPORT=LCDPORT | 0xF0;
LCDPORT=LCDPORT & temp;
LCDPORT=LCDPORT & 0x0F;

Remove the underlined line.

 

[yviswanathbe]

Hi d@nny and nandhu,

Thanks for your replies.

I have attached my schematic.

I have changed the code as nandhu said, but the result is same.

Pls help me in solving the problem.

Thanks and Regards,
Viswanath