[SOLVED] Issues with timers in assembly language (ATmega8)

Issues with timers in assembly language (ATmega8)

I've written a program for ATmega8 that outputs two different sounds, taken from two potentiometers.

The issue with that is, that a sound is generated by turning the beeper on and off with a delay in it, which is basically the value of the potentiometer.

But the higher the frequency is, the lower is the time the sound is played, and I want that the time the sound is played is unattached to its frequency.

So I decided to use a timer.

Planned is the following structure:

while(timer0counter > 0)
    while(timer2counter > 0)
        output on
    while(timer2counter > 0)
        output off

As you see, this should give a frequency over a specified time. The implementation so far looks as follows (PORTB is the beeper) (This is only for one sound):

mainloop:
    ldi r27,250;The value of one potentiometer, here a static value

    ldi r22,255
    mov r23,r27
    loop:

          ldi r16,4
          out PORTB,r16

          tst r23
          brne loop

          mov r23,r27

          inner:
                ldi r16,0
                out PORTB,r16

                tst r23
                brne inner

          tst r22
          brne loop

rjmp mainloop

While the timer overflow functions are:

tmr0overflow:
  tst r22
  breq skip0
  sub r22,1
  skip0:
reti

tmr2overflow:
      tst r23
      breq skip2
      sub r23,1
      skip2:
reti

Timer initialization:

ldi r16,5
out TCCR0,r16
ldi r16,2
out TCCR2,r16

ldi r16,(1<<TOIE0) | (1<<TOIE2)
out TIMSK,r16

I've also set the interrupt vectors for T2OVF, T0OVF and enabled interrupts in general.

But it doesn’t work. The output seems like random. what’s wrong with it?

Solution

Use:

;PORTC  0 = INPUT
;POT. 1[C0 / ADC0]
cbi     DDRC,0
cbi     DDRC,1
;PULLUP
sbi     DDRC,0
sbi     DDRC,1

The pull-up resistor is not set via the DDR, but the PORT. The input is not determined when reading from an output.