The problem is that I have to tell a part of the system to change volume.
By deafult this is done via Android API (AudioManager.adjustStreamVolume(...)) but on our unit the MCU deals with most of the sound setting. So it does with volume control.
That's why I had to talk to the MCU to adjust volume levels. I don't linke it but had no other chance.
Feel free to link to my posts if you feel it fits the thread. I will not for now as I do't really know.
I am currently thinking about asking XDA's staff to create a section for Car Headunits in general to have things a bit more sorted...
Then I wold create a Thread (or multiple)
Btw: If the App is not compatible and you can fiind out how to control volume programmatically I can patch my app!
Probably volume is not MCU-Controlled there? But that's offtopic. Please PN me for further discussions on that.