Interfacing 16x2 LCD with Atmega 32

Question

I am trying to interface 16x2 LCD display with atmega 32 in 4 bit mode and on display there's random character and black boxes. here below my code

//#define F_CPU 12000000UL #define F_CPU 11592000UL

#include <avr/io.h>
#include <util/delay.h>
#include <stdio.h>
#include "lcd.h"


#define LCD_DATA PORTD       // port D is selected as LCD data port
#define ctrl PORTB          // port B is selected as LCD command port
#define LCD_DPRT PORTD     // LCD DATA PORT
#define LCD_DDDR DDRD     // LCD DATA DDR
#define LCD_DPIN PIND    // LCD DATA PIN
#define LCD_CPRT PORTB  // LCD COMMAND PORT
#define LCD_CDDR DDRB  // LCD COMMAND DDR
#define LCD_CPIN PINB  // LCD COMMAND PIN
#define LCD_EN PINB2   // enable signal is connected to port B pin 0, same for given PCB 
#define LCD_RW PINB1  // read/write signal is connected to port B pin 1,-----------"----
#define LCD_RS PINB0 // register select signal is connected to port B pin 2, -----"-----

unsigned int adc_value; // Variable to hold ADC result

int main(void)
 { 

_delay_us(1);
_delay_us(1);  
DDRD=0xFF; // Port D is set for output 
DDRB=0xFF;  // port b is set command port 
_delay_us(20);       // 
//PORTA0=0x00;


/* Replace with your application code */
while (1)

{


    //*****************LCD INITIALIZATION**********************//
    lcd_initi(); 
    lcd_gotoxy(0,1);   // cursor location  in 1st row
    lcd_print("PCB NO:");
    lcd_gotoxy(1,2); // cursor location in 2nd row
    lcd_print("Verdict");
}

}    // main function end 



 //***********************************LCD FUNCTION DEFINATION's***************************//

//***************************************LCD COMMAND*************************************//

void lcdCommand (unsigned char cmnd) 

{  

    LCD_DPRT=cmnd; // Send command to data port a
    LCD_CPRT |=  (1<<LCD_RS); // Register select 
    LCD_CPRT &=  ~(1<<LCD_RW); // Read Select 
    LCD_CPRT |=  (1<<LCD_EN);    // Enable 
    _delay_us(20);       // Delay 
    LCD_CPRT &= ~ (1<<LCD_EN); // Enable  
   _delay_us(100);
}

//*********************DATA**********************//

void lcdData (unsigned char data )

{
    LCD_DPRT= data; // send data to data port
    LCD_CPRT |= (1<<LCD_RS);
    LCD_CPRT &= ~(1<<LCD_RW);
    LCD_CPRT |= (1<<LCD_EN);
    _delay_us(1);
    LCD_CPRT &= ~(1<<LCD_EN);
    _delay_us(100);
} 



 //*************************Initialize*************************//

void lcd_initi ()

{
    LCD_DDDR=0xFF;
    LCD_CDDR = 0xFF;

    LCD_CPRT &= ~ (1<<LCD_EN);   // LCD_EN = 0 //

    _delay_us(2000);   // wait for initialize 
    lcdCommand (0x33); // send $ 33 for inti
    lcdCommand (0x32); // display on , cursor on
    lcdCommand (0x28); //  4 bit mode,D4-D7
    lcdCommand (0x0e); // display on.cursor on
    lcdCommand (0x01); // clear lcd
    _delay_us(2000); // Delay 
    lcdCommand(0x06);  //shift cursor right

}


//**********************print string***************************************************// 

void  lcd_print(char*str)
{

    unsigned char i=0;
    while (str [i] != 0)
    {       
        lcdData (str[i]);
        i++;
    }
}

//************************************CURSOR SHUFFLING***************************************************//


void lcd_gotoxy (unsigned char x, unsigned char y )
{

    unsigned char firstcharadr []={0x80,0xC0,0x94,0xD4};
    lcdCommand (firstcharadr [y-1] +  x-1 ) ;
    _delay_us(1);

}



 //******************************ADC FUNCTIONS DEFINITION **********************************//

void ADC_init() 
{

//int adc_value;
ADMUX=(1<<REFS0); // For Aref=AVcc; 
ADCSRA=(1<<ADEN)|(1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0); // Set by ADPS Prescalar div factor =128 and Enable ADC //

}
void ADC_read()
{

ADCSRA|=(1<<ADSC);  // Start continuous conversion
while(!(ADCSRA & (1<<ADSC))); // wait for conversion to complete
adc_value = ADCW; // store adc value 
}

//************************************ KEY BUTTON ********************************************//

   void button ()
   {

   DDRA = DDRA & ~( 1<<6) ; //Make pin 6 of port A as a input

   //DDRA = DDRA & ~(1<<7) ; // Make pin 5 of port C as a input
   int button=0;

   while (1) //initialize while loop
   {
       if(PINA |= (1<<6) ) //if PIN5 of port A6 is high
       {
           lcd_gotoxy(0,8);
           lcd_print( button++);
       }
       else //otherwise
       {
           lcd_gotoxy(0,8); 
           lcd_print(button);    // value of PIN7 of port 7 will remain same 
        } 
        }    // while loop ends    
        }   // end of void function 

Answer 1

The lcd_print function appears to expect a char* -- a pointer to a null-terminated string of characters, typically in the range of printable characters (32 and above). It looks like your code is invoking the function directly with index i, which starts at zero and increases monotonically, if not linearly.

If the purpose is to print the value of the index variable, maybe try applying the itoa function to convert the index i to a character string before passing it into the lcd_print function.

Answer 2

There are multiple things wrong here. The lcdCommand and lcdData functions are meant for 8-bit transmissions as they transfer one byte per E pulse. This means that they can't be used when display is in 4-bit mode, and the initialization code will not set the display to 4-bit mode when using the 8-bit transmissions. They would have to be modified to send two 4-bit nibbles per E pulse. They also both set the RS pin high while during command transmission RS should be low.