Re: Fwd: Re: [avr-chat] Error in Timing.

[Royce Pereira]

Hi,
On Sun, 05 Mar 2006 00:52:57 +0530, Galen Seitz <address@hidden> wrote:

> > In fact, even with the internal RC osc, the accuracy was acceptable
> > for my app. (2 sec error in 20 mins). So I could do away with the
> > crystal(which I had added to solve this problem).
> >
> > Only inconvenience now is getting divisions to get 1ms,10ms. This was
> > possible with the prescaler at CK/8 (4000000/8 = 500000 i.e 0.5 ms, so
> > getting 10ms, 20ms was easy). Now I have prescaler at CK/256 giving
> > 15625 Hz, a non factor of 10 :(.
>
> It really sounds like you are doing this the hard way.  Is there
> something preventing you from using Timer 1 or 2.  These timers allow
> you to specify the value of TOP using an output compare register(CTC
> mode).  This makes it possible to get pretty much any interrupt rate.
> In your case, with the output of the prescaler at 500 KHz, you could set
> OCR2 to 249 and get an OCF2 interrupt every 500 us.
Well, I'm relatively new to AVR, and havnt bothered to delve into timer 1 operation (yet). 
Just wanted to get my project up & working & Timer0 was simpler to understand ;). I 
was quickly trying to port my 8051 knowledge to AVR, & Timer0 seemed similar in 
approach to Timer0 of 8051.

But of course you are right. I need to dig furthur into the data sheet !

Thanks,
--Royce.
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