Kenwood TM-D700a GPS-ificator

OK so you hack on a GPS to your existing car, drive around and the damn thing just isn't working. You've had a working APRS setup in your car for over a decade, two cars even at this point. Why did it stop working now?

Yeah okay so the puck you used to have just kind of has a dim solid red LED on it where it once briefly turned red then started green, then blinking green within a few seconds. Obviously, you just need another.

So you pick up a TTL serial GPS, knowing that radio was weird about GPSen. (But the GPS you have predates your decades old amazon account, so you can't just get an exact replacement)

GPS tech has come a long way since Kenwood designed this radio. The TM-D700a is a legendary 2 VFO dual band VHF/UHF moble with remote head. If I was in the market today, I'd get the same one, I don't care if they're discontinued, it's an absolute perfect rig for the application. If Kenwood TM-D7xxx models are adequate for the ISS, they're good enough for my car! Run the head and the mic up to the front seat, toss the radio under the floor in the hatch, and you're done. Add a junction box to tap in power between your anderson powerpoles, and you can add in a 5v regulator and get power for a GPS puck, and throw it in the 2.5mm GPS jack in the front. Full APRS support, dual VFO, what more could you want?

Documentation on that port would be a start! People have documented it on and off, but the important thing to know is the tip is your NMEA signal, and the sleeve is your signal ground. Shoot 4800 (or 9600 if you set it to NMEA96) NMEA data in there and you're good to go.

Except you have to make sure $GPn sentences go to it, $GNx ones get ignored, so if it's not sending $GPn you need to convert to $GNx to $GPn. Not a huge deal, the UBlox can do $GPn all day long. It can do 4800 or 9600 fine. So what's the issue?

You need RS-232 level signals :) That's where i realized I SCREWED UP and called in the ESP32 from the parts box. With some code, not only did I have a perfect output for the Kenwood, I had a fun bluetooth GPS with all the sentences for future hijinks

For power savings, the Bluetooth shuts off if stationary. You can configure that in the software. I've released it under the BSD 3 clause, if you need it under something else let me know, anything other than "I want to rip it off and call it my own" is fine. :)