Quote Originally Posted by xnihilo View Post
Sure, it is a lasergame system. the mag module performs a handshaking with the gun module. i.e. gun asks the mag if there are still ammo in the mag. if there are, the gun receives a signal and the ammo is used.

there are 2 pics 16f684 communicating. the mag ra5 is set as input and used at default low state (porta.5=0, wpu disabled).
when the gun sends a +5v to mag's ra5 for 1ms, mag then sets ra5 as output and it sends +5v out via ra5 to the gun as a reply then ra5 is set again as input at logic low. this ra5 pin is used as input/output for handshaking. TRISA is used to chang pin direction as needed.
so my trouble is, if i use an external 10k weak pulldown to avoid leaving it floating (and triggering a fake int on ra5 if there is some noise) i won't be able to disable the pull down in software when i'll be using the pin as output. do you see?
There should be no problem with using a 10k pull-down resistor. So the gun pin (the one that's connected to RA5 of the mag) goes to an input immediately after sending a 1ms high signal? This pull-down resistor would therefore stop the gun input pin floating as well.

Please correct me if I've mis-interpreted you

Cheers

Rob