Hey guys, I know this is a really old thread but I'm giving it a bump anyway in hopes that the OP might have an update on this. I'm doing a lot of searching around right now too to see what I can get figured out for something similar. To start out, I would like to just build a basic APRS tracking module that can radio back GPS position to my APRS iGate / Digi at home, which will then pass the data back to APRS-IS so I can see the module's path on APRS.FI, anyway, some of the things I'm finding seem like they would be great pieces to what I want to accomplish. The problem seems to be that once somebody figures out how to do this, they compile to a .HEX file and no longer have their sketches up anywhere. I have found a sketch and some instructions for getting an arduino board to talk to a GPS module, so that's a good start. The part I'm having trouble with is the radio side, actually getting the data transmitted.
Obviously, if you're going to do this, you will need a radio to transmit the data and a terminal node controller to format said data properly. Two options come to mind for the radio. You can pick up a cheap handheld for around $25 - $30 and interface it to the arduino, or you can go over to radiometrix and pick up whichever of their software defined radios best suits your needs.
So what specifically I am looking for right at the moment is the actual sketch that will have the arduino forming the APRS packet string and sending it to the radio. I need a sketch that will make the arduino into a TNC. I understand there are some components that need to be between the arduino and the radio and have that part worked out, it's just some resistors, capacitors and a transistor. Does anybody know of a sketch anywhere that will do this though?
To keep the code basic, lets assume for now that it will transmit callsign, six digit grid square, APRS icon, and a text string. Just like you would do in APRX as your beacon string. Assume for now that the electrical connections to a radio have already been made, and we just want to send a data signal out through the microphone connection of that radio. Even if all that string says is " Testing." I can figure out the rest from there.