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Thread: Measuring Frequency with a PIC
face BY : Dan Michaels email (remove spam text)

Brian Gregory wrote:
>Measuring Frequency with a PIC.
>I need to measure the frequency of a square(ish) wave at about 1000 - 1500Hz
>to about 20Hz resolution using a PIC16C710/711/715 PIC. Absolute accuracy is
>not required, I just need to check for an approx 90Hz change in input
>frequency from normal.
>Anybody got any ideas?

Take a look at Mchp appnote AN592.

>My first thought was to change to a PIC with a CCP unit and use that but
>when I read up on the CCP it doesn't look as if it's really that suitable.

With one of these PICs, 72/73/74/76/etc, you can simply use Timer1 as
a straight-forward 16-bit counter with prescaler, and Timer0 to clock
the duration of counting. Despite what the specs say about input signal
risetimes/periods [which is very confusing and has been revised several
times in the past couple of years], this channel will easily measure
pulse frequencies to over 50 Mhz.

hope this helps,
- Dan Michaels
Oricom Technologies

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