TMR1 counter debounce?


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  1. #1


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    If he is counting edges for some type of signal, a series R - shunt C filter may be better than the debounce filter. Just pick the 1/RC time constant to be higher than the max frequency of the signal you are trying to count, the nyquist freq (f*2) being a good starting point.
    Tim Barr

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    Thanks to every one for your help. Sorry for the delay in responding, our internet connection was down for 12 hours. I am trying to count the number of switch closures of a very fast reed switch. TMR1 is counting edges on T1CKI, just as it's supposed to. Ultimately,this switch will wake the program from SLEEP, and resume counting. I haven't as yet quite figured out how to use DT's Instant Interrupts to do this, but in doing so, maybe this will help with the "debounce" problem.

    For now, I may use Paul's idea of just counting the pin, or try using falingtrea's RC filter.

    Thanks again.

  3. #3
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    Red face

    I added debouncing for a switch to >> timer input of a F876 back in the day.

    I tried using a simple R/C network but found that the slow rise time of the signal as it was charging the capacitor back up violated the maximum rise time for the pic I/O.

    I ended up using the R/C filter but fed it into a schmidtt trigger prior to sending it to the timer I/O.

    This took care of things, I routinely test my devices by having another pic activate a relay thousands of times and test to see that the receiving pic counted correctly.

    fwiw

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