I understand this is quite a simple and more of a hardware question but I am having a very niggling problem.

I am using a development kit (the siLabs F060 dk) and connecting hardware to it via a breadboard and some molex connectors and ribbon cables. When using a button on the board (there is a single "PTM" switch on board) an if statement polling port 1 then carries out a function using outputs from port 3. The switch on bread board has the exact component values as that on the development board. It may be worth mentioning it has a pull up resistor, and a 0.1 microF capacitor for debouncing.

The problem is that the switch on the board works EVERY time i press it, where as the breadboard switch does not. I can see some noise at the outputs of the pins when pressing the switches on the breadboard but not when the switch is pressed on the devboard. I cannot work out the reason for this! My only theory is its something to do with the fact that it is connected through a molex connector and ribbon cable, but I can see the voltage change from 3V to 26mV at the resistor/switch output. (I cannot get a probe in at the end of the cable connected to the devboard).

I am using two different power supplies, and the power supply cable to the devboard too. Of course the ground on each supply has been connected. One supply is at 24V and supplies some relays, this also has a 10V Zener diode for some special switches which require 10V. The second supply is at 3.3V for the interfacing electronics for the inputs/outputs of the micro controller. I don't know if any of this last paragraph is of significance to my problem.

Cheers for any light you can shed on this odd problem!

Could it also be something to do with using 3 power supplies? Perhaps I should draw the power for the interfacing electronics from the ground and 3V3 lines that are at each port connection on the development kit.