There's probably more to it than that, such as noise in other parts of=20
the circuit that can be picked up by your digital input.  I have=20
circuits where 100k works very well (thousands of them built).

Cheers,
-Neil.



On 4/3/2013 1:46 PM, Allen Mulvey wrote:
> Sorry, this is my first post. I forgot to tag the subject
> line.
>
>  =20
>
> Is there a way to compute the optimum value of pull up (or
>
> pull down) resistors on PIC digital inputs?
>
>  =20
>
> Most example circuits I have seen seem to use 10k. My
>
> EasyPIC7 board uses 4k7. I have been experimenting and 20k
>
> resistors produce unreliable results. I don't see anything
>
> in the data sheet to help with this.
>
>  =20
>
> I am using a pic16f877a. The leakage current is one
>
> micro-amp. Sampling the port must draw considerably more. My
>
> current project is not battery operated but, if it were, I
>
> would like to use the largest resistors possible.
>
>  =20
>
> Thanks,
>
>  =20
>
> Allen
>
>  =20
>

--=20
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