AVR-Chat

Yes, declare variables accessed by both interrupt and non-interrupt as
volatile.
If the variable is two or more bytes in size (on the 8 bit AVR), then be
sure that the non-interrupt level code does something like this
cli();
<read or modify multi-byte variable used also by ISR>
sei();

And lastly, in the interrupt code, we want it fast. So here's
optimization one normally does:

...
if (++seconds == 60)  {
     seconds = 0;
     if (++minutes == 60)   {
         minutes = 0;
         if (++hours == 24)
            minutes = 0;
     }
}


--- In AVR-Chat@yahoogroups.com, Cat C <catalin_cluj@...> wrote:
>
>
> You're not showing where you declared "seconds" but make it volatile
and it will work:
>
> volatile uint8_t seconds;
>
> Cat
>
> ----------------------------------------
> > To: AVR-Chat@yahoogroups.com
> > From: ajellisuk@...
> > Date: Sat, 8 May 2010 17:54:29 +0000
> > Subject: [AVR-Chat] My timer does not seem to be incrementing an
integer
> >
> > Hi,
> >
> > I have a project using an Atmega16 where the timer should be
interrupting once a second, but my sconds variable in not being
incremented. If I use this line:
> >
> > PORTD = ~PORTD;
> >
> > The leds connected to that port flash, if I write my seconds
variable to that port only bianry one is indicated, whcih suggests to me
that the timer is not running or the firmware is being reset.
> >
> > Could someone shed some light on this for me please? I have disabled
the watch dog timer too My code is below:
> >
> > Andrew
> >
> > const uint16_t interval = 4000000/65536;//Work out interval from CPU
frequency
> >
> > void Init_Timer1()
> > {
> > // Set up counter. Fclk = 4Mz
> > TCCR1B = 1 << WGM12 | 1 << CS12; // Fclk / 256, clear on match
> > OCR1A = interval; // Timer ticks at 4000000/(256*interval) (1s)
> > TIMSK |= (1 << OCIE1A | 1 << TOIE1);
> > asm("sei");
> > }
> >
> > ISR(TIMER1_COMPA_vect)
> > {
> > wdt_reset();
> > power_save_timer++;
> > seconds = seconds+1;
> > PORTD = seconds << 2;// Used to verify timer is running
> >
> > if (seconds>59)
> > {
> > seconds=0;
> > minutes++;
> > }
> >
> > if(minutes>59)
> > {
> > minutes=0;
> > hours++;
> > }
> >
> > if(hours>23) hours=0;
> > }
> >
> >
> >
> >
> > ------------------------------------
> >
> > Yahoo! Groups Links
> >
> >
> >
>



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