KPL wrote:

> For now, I am looking for some description about frequency measuring. I
> see a lot of PIC-based F counters with asm code, but that code usually
> is overloaded with display management and other stuff so are quite hard
> to understand. Do anybody know any reference where I could read some
> good description _how_ to do that.

Don't know, but this might help you... Basically, you compare the frequency
to measure with a known frequency (which usually is the processor's clock). 

There are two main ways. One is to count how many cycles of the frequency
to measure fall within a known time; for example one second. You can use
e.g. the timer 1 in counter mode for this. This method is generally used
when the measuring time is (or may be) long compared to the cycle time.

The other method is to count how many cycles of the known frequency fall
within a single cycle (or a known multiple of a single cycle) of the
frequency to measure. You can use e.g. the CCP module in capture mode for
this. This is generally used when the frequency to measure is low compared
to the known frequency.

Which method you choose depends on the frequencies you're looking at, on
the precision and timing requirements, on the available hardware resources
-- and on personal taste :)  Sometimes you may want to switch between
methods based on a preliminary first result.

Gerhard

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist