hi... i am still very new here.....

i have a question, which should be very basic to all of you.

what i ask is that how to change duty cycle in PWM. i know we need to
update the value of CCRx to match the counter value.

this is done in one PWM cycle. what if i wanna change this CCRx value
for next PWM cycle to have other Duty Cycle? is it done by software or
hardware?

what i guess is that the very last overflow of one pwm cycle generates
interrupt that is fed to execute software line to write a new value to
CCRx. is it correct?

and how can we know the exact value to a certain Duty Cycle to generate?
for example, i wanna to have duty cycle from 30% 50% 55% 60% 62%. the
values for each duty cycle are already defined somewhere (like a table
to refer) and software reads them to write?

Please help me out with this questions...

Thanks in advance.

sonny


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Set the timer value to determine the period and the capture value to
determine the duty cycle.

Generally these two values are stored in RAM by the applications software. A
Timer
overflow reads the two values and sets the timer register to the period and
the capture
register to the duty cycle.

You could use a table but that is not very efficient. If you want 50% just
shift period value right once
and put it in the capture register.

Crane

mazeltob wrote:
>
> hi... i am still very new here.....
>
> i have a question, which should be very basic to all of you.
>
> what i ask is that how to change duty cycle in PWM. i know we need to
> update the value of CCRx to match the counter value.
>
> this is done in one PWM cycle. what if i wanna change this CCRx value
> for next PWM cycle to have other Duty Cycle? is it done by software or
> hardware?
>
> what i guess is that the very last overflow of one pwm cycle generates
> interrupt that is fed to execute software line to write a new value to
> CCRx. is it correct?
>
> and how can we know the exact value to a certain Duty Cycle to generate?
> for example, i wanna to have duty cycle from 30% 50% 55% 60% 62%. the
> values for each duty cycle are already defined somewhere (like a table
> to refer) and software reads them to write?
>
> Please help me out with this questions...
>
> Thanks in advance.
>
> sonny
>

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