I have spent several days researching and modifying code to be able to read the keypresses on a 4x3 matrix keypad. I see that it has been done a gazillion times and I guess there is something that I am just not grasping. I have downloaded several different versions, modified them for the microcontroler I am using, ATMega168A, and I have not been sucessful in getting any of them to work. After trying several modifications on each one to get one to work without success, I decided to pick one and just move forward with that method. I selected a version posted by Bob Gardner as he seems pretty knowlegable and his code looked like it would be fairly easy to modify to work as I needed. If there are others, I am open to suggestion.
So my process was to get the code from Bob to work first. I modified the code to address the correct port for the keypad and then set up an LED to toggle each time a key was identified for testing purposes. I loaded the code and then applied a jumper from PIND0 to PIND3 (which should correspond to C0 and R0 which is #0 ??) The LED should toggle each time the jumper is applied but I didn't get any response. So then I went to the debugger (Atmel Studio 6) and stepped through the code. Watching PINB1, it kept toggling on and off without supplying any input.
So I don't know where the problem is. Here is the modified code:
#include<avr/io.h>
char keytab[16]={
// 0 1 2 3 <-col
'C','D','E','F', //3
'8','9','A','B', //2
'4','5','6','7', //1
'0','1','2','3' //0 <-row
};
char getkp(void){
//return key pressed on pad outs lo nib, in hi nib
unsigned char c,row,col,rowcode,keyndx;
for(col=0; col < 4; col++){
PORTD &= ~(0x80 >> col); //out 0,1,2,3 lo
asm volatile("nop");
asm volatile("nop");
rowcode=PIND & 0x0F; //7,b,d,e=row 0,1,2,3
PORTD |= 0xff; //all outs off
// cprintf(" % 02x\n",rowcode);
if(rowcode != 0x0F) break; //this col has a row lo
}
if(rowcode == 0x0F){
c=0xff;
}else{
switch(rowcode){
case 0x07: row=3; break;
case 0x0b: row=2; break;
case 0x0d: row=1; break;
case 0x0e: row=0; break;
}//switch
keyndx=col*4 + row;
c=keytab[keyndx];
}
// cprintf("% 02x % 02x % 02x % 02x\n",rowcode,row,col,keyndx);
return(c);
}
int main (void){
DDRB=0xFF;
PORTB=0xFF;
for(;;){
char keyCode=getkp();
switch(keyCode){
case 0:
PORTB ^=1<<PINB1;
break;
case 1:
PORTB ^=1<<PINB2;
break;
}
}
}
When stepping through the code I noticed a couple strange issues.
These lines
rowcode=PIND & 0x0F; //7,b,d,e=row 0,1,2,3 if(rowcode != 0x0F) break; //this col has a row lo
So if I understand correctly, without any buttons being pressed, the value of PIND will be 0x00 and then PIND & 0x0F (to check for a value on PIND0-PIND3?) will make PIND still 0x00. Then the if statement is testing for rowcode (0x00) == 0x0F seems to pass the test. Maybe I am not understanding the degugger as it jumps around.
and if I type in the immediate window to print getkp() I get an error...Call to unknown function:getkp
What do I need to do to get this working?
