TMR1 counter debounce?

[paul borgmeier]

>> Temp var TMR1H

possibly part of the problem ... this gets redeclared each time through the "loop". You might want to move it up above where your other declaration resides.

[paul borgmeier]

>>My 16F689 TMR1 counter is counting too well

After sleeping on your question, it sounds like you need a hardware debounce filter, possibly like

http://www.elexp.com/t_bounc.htm

I do not know how to add one in software when using the TMR1 as a counter. You could switch to another software means of counting all together (e.g., Interrupt on change of one of the port pins, etc) where adding software debounce would be a piece of cake.

[falingtrea]

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.

[jderson]

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.

[Steve_88]

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