piclist 2001\01\18\154511a >
Thread: Reading Outputs as Inputs
face BY : Dan Michaels email (remove spam text)

Shawn Yates wrote:

>I am trying to avoing the adding of a pull-up.  Till now, the pin had no
>purpose.  It is not connected to any circuitry except for a header.  Now I
>want to use that pin as an input to allow the user to select a setting (by
>shorting or not shorting the header to power or ground.

Shawn, you have now discovered the reason I always recommend
tying a pulldown [or pullup] on every single unused pin on a
processor, rather than using one of the alternate schemes
[config as output/short to gnd/etc/etc/etc/etc] others have
mentioned recently on other threads.

Additionally, I would strongly recommend using a [small value]
series R inline in pins going to a header. Otherwise, too
durn easy to fry a pin with overvoltage or ESD, or short
an output. Been there, done that, replaced chips [not

- danM

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See also: www.piclist.com/techref/microchip/ios.htm?key=input
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