Ur help is needed in interfacing 4x4 keypad

[praveen_palaparthi]

hi friends i tried to interface 4x4 matrix keypad to pic 16f877 can any give me the source code in C to check which key is pressed


this is the code i have tried in hitech pic C complier
/*****************MAIN PROGRAM*****************/
main()
{
unsigned char i;
unsigned char key_pad[4][4]={ {'D','E','F',0},{9,'A','B','C'},{5,6,7,8},{1,2,3,4} };
OPTION=0x00; //enable pull up resistors by individual latch values
INTCON=0xC8; // enable Port B change interrupt
lcd(); //LCD intialization
keypad_matrix(); //4x4 matrix keypad intialization
while(1)
{
PORTB=0xF0; //All inputs are pulled to high
RA4=1;
PORTE= 0x07; // All outputs are pulled high
for(i=0;i<=3;i++)
{
switch(i)
{
case 0:
RA4=0;
if(RB4==0) //checking input is low
lcd_display(key_pad[0][0]);
else if(RB5==0)
lcd_display(key_pad[1][0]);
else if(RB6==0)
lcd_display(key_pad[2][0]);
if(RB7==0)
lcd_display(key_pad[3][0]);

break;
case 1:
RE0=0;
if(RB4==0) //checking input is low
lcd_display(key_pad[0][1]);
else if(RB5==0)
lcd_display(key_pad[1][1]);
else if(RB6==0)
lcd_display(key_pad[2][1]);
if(RB7==0)
lcd_display(key_pad[3][1]); //checking input is low
break;
case 2:
RE1=0;
if(RB4==0) //checking input is low
lcd_display(key_pad[0][2]);
else if(RB5==0)
lcd_display(key_pad[1][2]);
else if(RB6==0)
lcd_display(key_pad[2][2]);
if(RB7==0)
lcd_display(key_pad[3][2]); //checking input is low
break;
case 3:
RE2=0;
if(RB4==0) //checking input is low
lcd_display(key_pad[0][3]);
else if(RB5==0)
lcd_display(key_pad[1][3]);
else if(RB6==0)
lcd_display(key_pad[2][3]);
if(RB7==0)
lcd_display(key_pad[3][3]); //checking input is low
break;
}

}
}
}


void interrupt portb_change(void)
{
if(RBIF)
{
RBIF=0;
PORTB=0xF0; //All inputs are pulled to high
RA4=1;
PORTE= 0x07; // All outputs are pulled high
}
}

/************ROUTINES*********************************/

#include<pic.h>
#include "key.h"
#include "delay.h"
#define LCD_RS RB4
#define LCD_RW RB5
#define LCD_E RA2
#define LCD_DATA PORTB
#define LCD_STROBE ((LCD_E=1),(LCD_E=0))

__CONFIG(XT & WDTDIS & LVPDIS & UNPROTECT);

void lcd(void)
{
TRISB=0xC0;
PORTB=0;
lcd_init();
lcd_clear();
}
void lcd_init(void)
{

LCD_RS=0;
LCD_RW=0;
LCD_E=0;
DelayMs(40);
LCD_DATA=0x03;
DelayMs(5);
LCD_DATA=0x03;
DelayUs(100);
LCD_DATA=0x03;
DelayUs(40);
LCD_DATA=0x02;
DelayUs(40);
lcd_write(0x20);
DelayUs(40);
lcd_write(0x08);
DelayUs(40);
lcd_write(0x0F);
lcd_write(0x06);
DelayUs(40);
}

void lcd_clear(void)
{
LCD_RS=0;
lcd_write(0x01);
LCD_STROBE;
}

void lcd_write(unsigned char c)
{
DelayUs(40);
LCD_DATA = ((c>>4) & 0x0F);
LCD_STROBE;
LCD_DATA = (c & 0x0F);
LCD_STROBE;
}

void keypad_matrix(void)
{
TRISB=0xF0; //RB7:RB4 are taken as input
TRISA=0xEF; //RA4 is taken as output
TRISE=0xF8; // RE2:RE0 is taken as output


}

void lcd_display(unsigned char c) // displays data on LCD
{
lcd_goto(0x07);
DelayMs(5);
LCD_DATA = 0;
LCD_RS = 1;
LCD_DATA |= ( ( c >> 4 ) & 0x0F );
LCD_STROBE; //high to low pulse must be applied in order for the LCD to latch in the data
LCD_DATA &= 0xF0;
LCD_DATA |= ( c & 0x0F );
LCD_STROBE;
LCD_RS=0;
}

void lcd_goto(unsigned char pos)
{
LCD_RS=0;
lcd_write(0x80+pos);
}

 

[sohailkhanonline]

//Keypad connection:
#define ROW0 PIN_A0
#define ROW1 PIN_A1
#define ROW2 PIN_A2
#define ROW3 PIN_A3
#define COL0 PIN_C0
#define COL1 PIN_C1
#define COL2 PIN_C2
#define COL3 PIN_C3

// Keypad layout:
int const KEYS[4][4] =
{{'1','2','3','A'},
{'4','5','6','B'},
{'7','8','9','C'},
{'*','0','#','D'}};

#define KBD_DEBOUNCE_FACTOR 33

short int ROW_HIGH()
{
if(input (ROW0) || input (ROW1) || input (ROW2) || input (ROW3))
return (1);
else
{
return (0);
}
}

char kbd_getc()
{
static byte kbd_call_count;
static short int kbd_down;
static char last_key;
static byte col;

byte kchar;
byte row;

kchar='\0';

if(++kbd_call_count>KBD_DEBOUNCE_FACTOR)
{
switch (col)
{
case 0:
output_high(col0);
output_low(col1);
output_low(col2);
output_low(col3);
break;

case 1:
output_low(col0);
output_high(col1);
output_low(col2);
output_low(col3);
break;

case 2:
output_low(col0);
output_low(col1);
output_high(col2);
output_low(col3);
break;

case 3:
output_low(col0);
output_low(col1);
output_low(col2);
output_high(col3);
break;
}

if(kbd_down)
{
if(!ROW_HIGH())
{
kbd_down=false;
kchar=last_key;
last_key='\0';
}
}
else
{
if(ROW_HIGH())
{
if(input (row0))
row=0;
else if(input (row1))
row=1;
else if(input (row2))
row=2;
else if(input (row3))
row=3;
last_key =KEYS[row][col];
kbd_down = true;
}
else
{
++col;
if(col==4)
col=0;
}
}
kbd_call_count=0;
}
return(kchar);
}

//===========================
void main()
{
char k;

printf("\r\Starting ...");

while(TRUE)
{
k=kbd_getc();
if(k!=0)
{
if(k=='*')
printf("%c", '*');
else
printf("%c", k);
}
}
}

Its CCS code

 

[ckshivaram]

// program for 4x4 matrix. using 89c52. PLease confirm the portpins of the
//hardware before running it. using 4 bit LCD
#include<reg51.h>
#include<intrins.h>

sbit rs=P0^0;
sbit en=P0^1;

void cmdwrt();
void delay();
void datawrt();
void mdata();

unsigned char dis[8]={0x20,0x20,0x28,0x0f,0x01,0x06,0x80};
unsigned char a;

main()
{
int i;
for( i=0;i<8;i++)
{
a=dis;
cmdwrt();
delay(); delay();
}
while(1)
{
P1=0x78;
a=P1;
if(a == 0x70)
{
a='0';
delay(); delay();
datawrt();
delay(); delay();
}

P1=0x74;
a=P1;
if(a == 0x70)
{
a='1';
delay(); delay();
datawrt();
delay(); delay();
}

P1=0x72;
a=P1;
if(a == 0x70)
{
a='2';
delay(); delay();
datawrt();
delay(); delay();
}

P1=0x71;
a=P1;
if(a == 0x70)
{
a='3';
delay(); delay();
datawrt();
delay(); delay();
}

P1=0xb8;
a=P1;
if(a == 0xb0)
{
a='4';
delay(); delay();
datawrt();
delay(); delay();
}

P1=0xb4;
a=P1;
if(a == 0xb0)
{
a='5';
delay(); delay();
datawrt();
delay(); delay();
}

P1=0xb2;
a=P1;
if(a == 0xb0)
{
a='6';
delay(); delay();
datawrt();
delay(); delay();
}

P1=0xb1;
a=P1;
if(a == 0xb0)
{
a='7';
delay(); delay();
datawrt();
delay(); delay();
}

P1=0xd8;
a=P1;
if(a == 0xd0)
{
a='8';
delay(); delay();
datawrt();
delay(); delay();
}

P1=0xd4;
a=P1;
if(a == 0xd0)
{
a='9';
delay(); delay();
datawrt();
delay(); delay();
}

P1=0xd2;
a=P1;
if(a == 0xd0)
{
a='A';
delay(); delay();
datawrt();
delay(); delay();
}

P1=0xd1;
a=P1;
if(a == 0xd0)
{
a='B';
delay(); delay();
datawrt();
delay(); delay();
}

P1=0xe8;
a=P1;
if(a == 0xe0)
{
a='C';
delay(); delay();
datawrt();
delay(); delay();
}

P1=0xe4;
a=P1;
if(a == 0xe0)
{
a='D';
delay(); delay();
datawrt();
delay(); delay();
}


P1=0xe2;
a=P1;
if(a == 0xe0)
{
a='E';
delay(); delay();
datawrt();
delay(); delay();
}


P1=0xe1;
a=P1;
if(a == 0xe0)
{
a='F';
delay(); delay();
datawrt();
delay(); delay();
}

}
}

void cmdwrt()
{
unsigned char s=0;
s=a;
a=a & 0xf0;
a=a>>2;
rs=0;
//mdata();
//delay(); delay();
P0=a;
rs=0;
en=1;
en=0;
a=s;
a=(a<<4);
a=a & 0xf0;
a=a>>2;
rs=0;
//mdata();
P0=a;
rs=0;
en=1;
en=0;
delay(); delay();
}

void datawrt()
{
unsigned char s=0;
s=a;
a=a & 0xf0;
a=a>>2;
rs=1;
//mdata();
//delay(); delay();
P0=a;
rs=1;
en=1;
en=0;
a=s;
a=a<<4;
a=a & 0xf0;
a=a>>2;
rs=1;
//mdata();
P0=a;
rs=1;
en=1;
en=0;
delay(); delay();
}





void delay()
{
int i;
for(i=0;i<9000;i++);
}