Hi, I've developed a frecuency counter that counts from 0 to 720Hz for a motor driver. I've used, to acomplish that, the math routines from some app note from microchip.
        An important thing is that (I dont know why) it didn't work well at the
first time, so I've had to make some corrections to it in order to make it work well (I speak english realy bad, don't I)
        Well, the thing is that the frecuency I was measuring was very unstable, and I needed to "read" the frecuency for a more than a second to have an stable reading.
        I used for this a PIC16C63 (very big for such a thing but I'll add some
features to it) and the board is smaller than a credit card and it cost only U$S 15.
        If you are realy interested on this I can send you a brief explaining how this circuit and code works; the only thing you must do is be patient, cause it will take me a few days to do this job cause I dont have much time.

        Hope I've been usefull, MAURICIO JANCIC

-----Mensaje original-----
De:     Lea [SMTP:lu2aoq@YAHOO.COM]
Enviado el:     Martes, 02 de Noviembre de 1999 10:43 p.m.
Para:   PICLIST@MITVMA.MIT.EDU
Asunto: Low freq. frecuency counter howto?

        Hi All
Can someone give me an idea about how to do a Low frequency , frecuency
counter?, I need to count between 50 Hz and 300 Hz, but not more than that,
and if it's possible avoid interference from higher frecuencies.
I need it to detect CTCSS tones from a given radio channel, so it must have
less than 2 Hz of error, it is possible to do it with a F84??.
Thanks in advance.
   Leandro J. Laporta (LU2AOQ)
   mail: lu2aoq@yahoo.com
   wrk: Arg. Assoc. for Space Technology.
   ham: TCP/IP high speed group HSG