Martix Keypad Interfacing with Microcontrollers: AVR Programming
►Programming AVR Microcontroller ►AVR Assembly Programming for ADC0804CODE:
.include "8515def.inc"
.equ col1 = PINA0
.equ col2 = PINA1
.equ col3 = PINA2
.equ col4 = PINA3
.def keyval = r16
.def temp = r17
.def flags = r18
.equ keyport = PORTA
.equ pressed = 0
key_init:
ldi keyval,$F0 ;Make Cols as i/p
out DDRA, keyval ;and Rows as o/p
ldi keyval,$0F ;Enable pullups
out keyport, keyval ;on columns
ret
get_key:
ldi keyval,$0 ;Scanning Row1
ldi temp,$7F ;Make Row1 low
out keyport,temp ;Send to keyport
rcall read_col ;Read Columns
sbrc flags,pressed ;If key pressed
rjmp done ;Exit the routine
ldi keyval,$4 ;Scanning Row2
ldi temp,$BF ;Make Row2 Low
out keyport,temp ;Send to keyport
rcall read_col ;Read Columns
sbrc flags,pressed ;If key pressed
rjmp done ;Exit from routine
ldi keyval,$8 ;Scanning Row3
ldi temp,$DF ;Make Row3 Low
out keyport,temp ;Send to keyport
rcall read_col ;Read columns
sbrc flags,pressed ;If key pressed
rjmp done ;Exit the routine
ldi keyval,$C ;Scanning Row4
ldi temp,$EF ;Make Row4 Low
out keyport,temp ;send to keyport
rcall read_col ;Read columns
done:
ret
read_col:
cbr flags, (1<<pressed) ;Clear status flag
sbic PINA, col1 ;Check COL1
rjmp nextcol ;Go to COL2 if not low
hold:
sbis PINA, col1 ;Wait for key release
rjmp hold
sbr flags, (1<<pressed) ;Set status flag
ret ;key 1 pressed
nextcol:
sbic PINA,col2 ;Check COL2
rjmp nextcol1 ;Goto COL3 if not low
hold1:
sbis PINA, col2 ;Wait for key release
rjmp hold1
inc keyval ;Key 2 pressed
sbr flags,(1<<pressed) ;Set status flag
ret
nextcol1:
sbic PINA,col3 ;Check COL3
rjmp nextcol2 ;Goto COL4 if no pressed
hold2:
sbis PINA, col3 ;Wait for key release
rjmp hold2
inc keyval ;Key 3 pressed
inc keyval
sbr flags, (1<<pressed) ;Set status flag
ret
nextcol2:
sbic PINA,col4 ;Check COL4
rjmp exit ;Exit if not low
hold3:
sbis PINA, col4 ;Wait for key release
rjmp hold3
inc keyval ;Key 4 Pressed
inc keyval
inc keyval
sbr flags, (1<<pressed) ;Set status flag
ret
exit:
clr keyval ;reset keyval
cbr flags, (1<<pressed) ;No Key Pressed
ret
CODE:
#include <avr/io.h> // Include file for AVR
#define keyport PORTA //Keypad Port
#define keyportddr DDRA //Data Direction Register
#define keyportpin PINA //Keypad Port Pins
#define col1 PA0 //Column1 PortA.0
#define col2 PA1 //Column2 PortA.1
#define col3 PA2 //Column3 PortA.2
#define col4 PA3 //Column4 PortA.3
#define TRUE 1
#define FALSE 0
unsigned char keyval; //A variable
/*
+---------------------------------------+
| Prototype: void key_init(void); |
| Return Type: void |
| Arguments: None |
| Description: Initialize ports and |
| Keypad. |
+---------------------------------------+
*/
void key_init(){
keyportddr = 0xF0;
keyport = 0x0F;
}
/*
+-----------------------------------------------+
| Prototype: unsigned char get_key(void); |
| Return Type: unsigned char |
| Arguments: None |
| Description: To read key from the keypad |
+-----------------------------------------------+
*/
unsigned char get_key(){
unsigned char i,key=1;
for(i=0;i<4;i++){ //Loop for 4 rows
keyport &=~(0x80>>i); //Make rows low one by one
if(!(keyportpin & (1<<col1))){
//check COL1
while(!(keyportpin & (1<<col1)));
//wait for release
return key;
//return pressed key value
}
if(!(keyportpin & (1<<col2))){
//Check COL2
key += 1;
//Second key pressed
while(!(keyportpin & (1<<col2)));
//wait for release
return key;
//return key value
}
if(!(keyportpin & (1<<col3))){
//Check COL3
key += 2;
//Third key pressed
while(!(keyportpin & (1<<col3)));
//Wait for release
return key;
//Return value
}
if(!(keyportpin & (1<<col4))){
//check COL4
key += 3;
//Fourth key pressed
while(!(keyportpin & (1<<col4)));
//Wait for release
return key;
//Return key value
}
key +=4; //Next row
keyport |= 0x80>>i;
//make read row high again
}
return FALSE; //return false if no key pressed
}
The next section of the tutorial will cover the programming of 8051.
◄ Connecting a Keypad | 8051 Program ►
This work is licensed under a
