Re: [avr-libc-dev] new to avr-libc programming: interrupt handling

[Joerg Wunsch]

As address@hidden wrote:

> how it looks:
>   outp( 0x37, TCCR0 ); /* set TCCR timer/counter control register to 
> prescaled 
> clock of 1/256 and sets OCF0 on compare match*/

Hmm, better use

        TCCR0 = 0x37;

now.  That's the prefered syntax.  If i were you, i'd rather use

        TCCR0 = _BV(COM00) | _BV(COM01) | _BV(CS02) | _BV(CS01);

That makes it more obvious that your description didn't match your hex
values :) (clk/256 vs. clk/1024).

>   outp( 0x2, TIFR ); /* OCF is cleared when executing the interupt handlig 
> vector */

That's not necessary.  The flag is cleared by hardware anyway.

>   outp( 0x2, TIMSK ); /* OCIE is set -> otput compare interrupt enabled */
> 
> 
>   sei(); /* is this right? do I need more method calls to let the program 
> listen to an interrupt? */

That's OK.

> //interrupt method definition:
> interrupt [TIM0_COMP] void time_out( void ) { }

RTFM. :-)  You can find TFM here:

http://savannah.nongnu.org/download/avr-libc/doc/avr-libc-user-manual/

More specifically:

http://savannah.nongnu.org/download/avr-libc/doc/avr-libc-user-manual/group__avr__interrupts.html

So in your case

SIGNAL(SIG_OVERFLOW0)
{
   ...
}
-- 
J"org Wunsch                                           Unix support engineer
address@hidden        http://www.interface-systems.de/~j/