AVR-Chat

Marc R.J. Brevoort wrote:
>>> Right now, I've set:
>>> TCCR0B = 0<<CS02|0<<CS01|1<<CS00 (no prescaling)
>>> TCNT0 = 255 (overflow on next tick)
>>> TIMSK=(1<<TOIE) (enable counter overflow int).
>>>       
>
>   
>>    For one interrupt every 1/31250Hz, I'd use:
>>    TCCR0A = 1<<WGM1  (CTC mode)
>>    TCCR0B = 1<<CS01   (8MHz/8)
>>    OCR0A = ((8MHz/8)/31250Hz)-1 = 32-1
>>    TIMSK = 1<<OC1E0A
>>    TCNT0 = don't care
>>     
>
> I assume you mean 1<<WGM01 for TCCR0A (CTC mode, TOP=OCR0A).
> I also changed ISR (SIG_OVERFLOW0) to ISR (TIMER0_COMPA_vect).
> This works, more or less. That is, the interrupt routine gets 
> called, but by the pitch I get it seems to be at a quarter of
> the rate that it should be.
>
> Strangely, altering OCR0A does not seem to influence
> the pitch at all, which makes me think something else is
> amiss which makes the ATtiny ignore the value in OCR0A.
>
> Any ideas?
>
> Best,
> Marc
>   

    Please verify if the clock source fuses are set up to cristal 
oscillator.
    Check CKSEL0 to CKSEL3 and CKDIV8.

    Mark Jordan