Phidgets and Transponder

Greetings!

I'm new here, and new to sim building, but after literally a year of research and googling, and reading everything I can find, I've made the decision to move forward. I know what I want, and now I'm starting to build. RIght now I'm sticking to just a simple C172 cockpit.

I have FS2Phidgets loaded up, and I've been trying to learn it, and figure things out. I have landing lights and basic switches working just fine. I want to try to build my own radio stack using Phidgets Text displays also.

The biggest thing I can't seem to understand how I would accomplish is the Transponder. Is there a way in FS2phidgets that I could define a series of digital inputs as the "number pad" for a transponder, and somehow keep track of which digits were pressed and pass that on to the transponder? Or define a "vfr" button that sends "1200" to the transponder?

Even simpler, I was trying to just see if I could pass a value to the transponder when I press a button - just all 4 digits at once as a proof of concept, and I can't seem to figure it out.

How do I increment the transponder digits? I'd even be ok with using 4 rotary encoders as long as I could change the digits, but right now I don't see how I can even do that.

I also keep reading about an FS2phidgets tutorial that is under the "help" menu. When I click help, nothing happens. Any ideas?

Thanks for all of the great information I've been able to pick up by lurking and reading thus-far.

Bill