Detect button on a ground line (reverse eng) I've found a circuit board that has a couple of circuits (buttons, IR Receiver, LED, USB). The thing is that following the line for interfacing the buttons I came across what seems to be like buttons that are connected only to the ground line of the PCB while the other end is a free pin cable.

Is there a way for the arduino to detect the ground when the button is pressed or a way to detect a short of some kind? There is a smd and a resistor on both buttons. 

Circuit:

Main Ground-----Button-----SMD Capacitor-----Resistor(101)-----Free Pin 

Thanks in advance!

Edit: Circuit Board
It sounds like you might have a PCB with debounced switches on them. One such circuit for debouncing switches looks like this:



That circuit and more about switch debouncing can be found here.

A debouncer basically masks the problem of switch "bounce" which is what happens when the contacts get close and the circuit is quickly closed and opened in rapid succession until a firm connection is obtained. Its a natural problem  mechanical switches.

If that's not quite right, maybe you could help us help you better by posting a photo of the board in question.