Closing Contacts with Raspberry Pi - novice question

[alfista]

Hi All,

I'm a long-time IT guy, but I don't have much of a background in electrical engineering beyond simple wiring. I've picked up a Raspberry Pi to tinker with and I have a project/challenge I'm excited about trying to solve.

I found an obscure AMS Alpha 216 LED sign from 1991 (Like BetaBrite) at a yard sale and it works great. It has a wired alphanumeric keypad for programming that connects via a 14 pin ribbon cable but programming it is somewhat painful. Specs on the pinouts are basically nonexistent. I'd like to be able to configure it for remote, WiFi programming.

I was figuring I could use the GPIO board to simulate keystrokes to the display and I have RPi and WiringPi installed and working and I'm not too worried about the coding side of things. I've also used a multimeter to identify the pin combinations that represent the different keystrokes from the keyboard.

Thus my question: I understand how to make a pin an output pin and send current to ground to complete a circuit but I can't figure out how to close a circuit between two pins where one is not a ground, essentially simulating the keystroke on the keypad. I am not sure if I need additional hardware to achieve this task but I'm having fun learning: old dog new tricks.

Can someone point me to a resource that might help?

If I've posted in the wrong forum or used the wrong terms I apologize in advance.

Cheers!

[Zener]

Most straightforward way is use relays. Here is an example that turns on the relay when your IO pin goes high:

http://playground.arduino.cc/uploads/Le ... relays.pdf