Hi
At first to awnser the master question..... Yes the firmware is puplished and available.
https://bitbucket.org/mobiflight/mobiflightfc/src/master/
This should also include the firmware, the upadeter and uploader system and the whole conncetor code.
About request.....
In Theroy this is possible.
You need to "copy" the way how the firmware recive data..... In your Arduino Sketch. Then this will work.
BUT
You should also think about alternates. In the time you do that maybe a other solution is more profitable.
"Andreas" sounds german. If Yes feel free to join Discord and talk to Sebastian, Stephan or Myself. Maybe a Brainstorming is verry usefull here.
If not german,.,,, English works well also,
Way 1. Simply disconnect your devices from the UNO and conncet it to a Mega. Should be no big deal. Cost some € for Megas but pretty sure much more faster as programming a own System.
Way 2. Using UNO with Mobiflight.... In Theory UNO is compatible.... But the Firmware is to large. So we stop this project. ( But the master code is still in the software).
Our target was to handle a UNO same way like a Mega.... So for User all is possible. That was a fault cause Memory is not enough to handle the firmware.
BUT in your case you not need the full firmware. If you not use LCD, / Seg etc. you can remove this parts.... And then the firmware should be compatible with UNO.
So... A rework of the exisiting MF system is maybe more easy as build a fully new one.
Way 3 Reverse Way.... Why think about a NEW Firmware on the UNO and using the esiting Mobiflight as "Data Creator" . Why do you not create a own Software on The Desktop ( alternate to Mobiflight) that just read the data from Sim and recalculate it.... and send it to your UNO same way like in the past.
You not need a GUI and experience there. This Software can run without a interface... All you need can be done within the code.