I don't see anything here that indicates an AUDIO =>TTL or TTL => AUDIO interface in your system.
Audio signals must be capacitively coupled and voltage biased to 2.5V to interface to an analog input.
The diagram wasn't meant to include everything, it was just to show where I think the two different types of signal modulation are happening, FM and FSK, to make sure I wasn't mixing them up. I do have a capacitively coupled receiver. The schematic was available in the link to the micromedem I said my circuit was based on, but it probably would have been better to post it here too.
I don't see any oscilloscope screenshots for inputs or outputs. (until later in your most recent posts)
Maybe you missed it, but in the previous posts before the scope shots, I mentioned that I didn't have a scope. I just bought my first oscilloscope and as soon as I learned how to use it I had those pictures up.
You certainly get an "A" for AMBITION, but I would give lower marks for planning and execution because you are interfacing very different types of circuit blocks.
I have the patience to screw up repeatedly. It's the most effective way for me to learn. It's more about the learning than the project anyway.
You probably think I am unfairly critical but that's because I am a professional electronics engineering technician and these kinds of projects are usually done with a lot more research in the commercial world so seeing this as a "hobby" project, it strikes as just "thrown together", rather than "carefully planned" and the forum posts strike me as sorely lacking in schematic reference detail.
Screwing around, tossing stuff together that shouldn't fit, inconsistent progress, and dead ends. All part of the amature/hobbiest experience. I am learning, and I'll take your advice to include every last detail, schematic, and line of code of my project when I make the next post.
I've seen the HX1 used in a number of high altitude balloon projects, like this one: APRS Micro-Trak 300 V1.3
Evidently the HX1 has a digital input but the internal modulation generates the required audio tones in the matching receiver, HRX1. So, the microModem tone generation code is not needed. It appears that you still have to assemble packets with preamble, sync, data and checksum.
To use the HX1, you need the matching receiver and to follow the manufacturer's or other people's advice on how to set up a functional communications system. I haven't done the research required in order to be of assistance.
The microModem software is better suited to handheld radios intended for voice communications.
So do I need to buy another radio? I was hoping to avoid that. Since all the APRS transmissions should be standardized, would I be able to keep the receiver I have and just change the code on the transmitter to just write all the right bits? The HX1 is made specifically for APRS, and If I can receive any other APRS packet on my micromodem/LibARPS receiver, I should be able to receive the packets from the HX1.
Is there a way to get LibARPS to give me the unparsed APRS packets, like a GPS can return NMEAs as they come?
Note that you need a license to operate the HX1.
I got it, they even made me give my call sign before I was allowed to buy it. I'll admit, I only studied for two hours before taking the test. I got almost every answer correct on the test, but it may have been too easy if it lets a dummy like me on the airways.