PIC18f452 port listening issue

Question

Why doesn't this code work? All that I want is portb to toggle when I press a button.

main
trisb=0
trisa=0xff
while true
if ra0<>0 then
portb = not portb
end if
wend .end

Answer 1

I'm not sure what that is; is it pseudocode?

Anyway, you need to trigger on the CHANGE from RA0 == 0 to RA0 == 1. As written, as long as RA0 == 1 then your PORTB will toggle every time through the loop.

Here's an example in C:

int main(void)
{
    unsigned char bButtonValue = 0;

    TRISA = 0xFF;
    TRISB = 0x00;

    while (1)
    {
        if (RA0 != bButtonValue) 
        {
            bButtonValue = RA0;
            if (bButtonValue == 1)
            {
                 PORTB= ~PORTB;
            }
         }
     }
}

Keep in mind that for a real app, you would want to debounce the switch input (make sure it's stable for a few samples before triggering the change event.