Pull down button on Port B

[Ioannis]

Ther only way high current may damage the input pin is by inducing that current from an external source. I do not know how is your settup exctly, but if you do have long wires or nearby high voltage cables, or even relays, motors etc, there could be a small chance of hurting that input.

You may:

1. put an external lower value pull-up resistor, say 470 ohm
2. put a capacitor in parallel with the switch but close to the pic input and gnd
3. add that 100 ohm resistor

In any case, if ESD is of concern, i'd not trust the 100 ohm resistor alone. Would use all 3 above.

Even better on the pic side of that 100 ohm at its pin, adding a ferrite ring would increase the resistance for fast spikes maybe up to 1K.

I had no problems up to this moment with just internal pull-up only, and with cable to the button less than 8cm. No false trigger or even port mulfunction.

Ioannis

[richard]

I had no problems up to this moment with just internal pull-up only, and with cable to the button less than 8cm. No false trigger or even port mulfunction.

keep in mind AN552 refers to ancient technology that has no esd protection of any kind [like esd diodes], with contemporary chips i would expect no trouble either.