Interfacing a 4x4 keypad matrix with Atmega32 - c

Question

I am trying to interface an Atmega32 micro-controller with a 16x2 LCD and a 4x4 keypad matrix. I am simulating with Proteus and using WinAVR compiler.
The LCD part is okay (I have thoroughly tested it). The keypad code, however, is not running as I expect. Whenever I press a key, the scanning of keypad rows stops indefinitely.
Also the key doesn't display on the LCD. Please help me find the bug.
Below is the circuit schematic as drawn in Proteus, as well as the code. I have not included code for the LCD here since I know that part is working perfectly well.
Circuit:
Code:
#include <avr/io.h>
#include<util/delay.h>
//Keypad Information
#define R0 0
#define R1 1
#define R2 2
#define R3 3
#define C0 4
#define C1 5
#define C2 6
#define C3 7
#define keypadPORT PORTA
#define keypadPIN PINA
#define keypadDDR DDRA
//Keypad functions and global variables
char getkey();
int keypadRow[] = {R0, R1, R2, R3}; //rows of the keypad
int keypadCol[] = {C0, C1, C2, C3};//columnd
int main()
{
char key_pressed;
keypadDDR |= (1<<R0)|(1<<R1)|(1<<R2)|(1<<R3);//set upper part of keypad port as output
//this will be required for scanning the rows
keypadDDR &= ~((1<<C0)|(1<<C1)|(1<<C2)|(1<<C3));//set lower part of keypad port as input.This is
//the part of the keypad port where the rows are connected.
LCD_init(); //initialize LCD
while(1)
{
key_pressed = getkey();
switch(key_pressed)
{
case('A'):
break;//do nothing if no key is pressed
default:
send_char(key_pressed);//send the key pressed to LCD
}
}
return 0;
}
char getkey()
{
int i, j;
for(i = 0; i < 4; i++)
{
keypadPORT = 0x00;
keypadPORT |= (1 << keypadRow[i]);//send a high to a particular row of the keypad
for(j = 0; j < 4; j++)
{
if(bit_is_set(keypadPIN,keypadCol[j]))//check if key is pressed
{
while(bit_is_set(keypadPIN,keypadCol[j])); //wait for key to be released
switch(i)
{
case(0):
{
if (j == 0) return '7';
else if (j == 1) return '8';
else if (j == 2) return '9';
else if (j == 3) return '/';
break;
}
case(1):
{
if (j == 0) return '4';
else if (j == 1) return '5';
else if (j == 2) return '6';
else if (j == 3) return '*';
break;
}
case(2):
{
if (j == 0) return '1';
else if (j == 1) return '2';
else if (j == 2) return '3';
else if (j == 3) return '-';
break;
}
case(3):
{
if (j == 0) return '?';
else if (j == 1) return '0';
else if (j == 2) return '=';
else if (j == 3) return '+';
break;
}
}
}
}
}
return 'A';//Return 'A' if no key is pressed.
}

Answer 1

If, whenever you press a key, "the scanning of keypad rows stops indefinitely" and "the key doesn't display on the LCD", then I'd be looking at any potential infinite loops, such as the following line:
while(bit_is_set(keypadPIN,keypadCol[j]));
I don't know whether the columns drain away to ground or stay high when you release the key but you should be able to check that behaviour by replacing that line with:
send_char('<');
while(bit_is_set(keypadPIN,keypadCol[j]));
send_char('>');
If you are indeed getting caught in an infinite loop there, the display should show you the <.