AVR-Chat

--- In AVR-Chat@yahoogroups.com, "Philippe Habib" <phabib@...> wrote:
>
> Thanks for the reply.  I looked through the data sheet for guidance
about
> the various counters but I wasn't able to figure out what I need.  Maybe
> someone here can help.
> 
> I am using an ATMega 128 clocked at 16 mhz.  What I'm trying to get is a
> 10khz PWM from timer 1 and a 2 khz pwm from timer2.  I am using the
Bascom
> BASIC.
> 
> I expect that what I need to do is to use these like I use timer0 to
set up
> my 10ms timer tick. For that, I set the prescale to 1024 and by
reloading
> the timer to 99 each time my timer ISR executes, I get a 10ms tick.
> 
> Since this is a PWM and I don't have an ISR, I'm looking for the way
to set
> that reload value one time when I configure the PWM.  That's what
I've been
> unable to find.
> 
> I have experimented with trying to set various timer related things but
> haven't gotten it to work.
> 
> Here are my declarations:
> 
> Config Timer0 = Timer , Prescale = 1024
> Config Timer1 = Pwm , Pwm = 10 , Compare A Pwm = Clear Up , Prescale = 1
> Config Timer2 = Pwm , Pwm = On , Compare Pwm = Clear Up , Prescale = 8
> 
> 
> I'd appreciate any help from someone who knows the answer on this one.
> 
> Thanks.
> 

Philippe:

I believe you need to use a PWM wave generation MODE that allows you
to specify the "TOP" value.  This value is specified in the OCRnA or
ICRn register.

While I haven't used an ATmega128, I did something similar with an
ATmega8 to generate a PWM signal for RC servo control.  I used timer1
in "fast PWM" mode, set the "TOP" value in the ICR1 register, and
adjusted the duty cycle by loading different values in the OCR1A
register.  I assume something similar can be accomplished with the
ATmega128.

Rick