At this time I`ve unlocked the protocol that is used to interchange between the Head Unit and Multi-CD. There is an emulator shown on my website. Briefly, it is a command conversion unit from IP-Bus into RS-232 and backward. So, HU can be easily connected to COM-port of just any PC.
But, if i did not misunderstood, you`re talking about the inverted task - to manage the HU from some kind of remote control (turn on/off, change the volume and so on). Unfortunately, I am not able to do this yet. This possibility exists, and this remote can be done, but I need some device with such ability to check out exactly how it works.
Since I have the CD-changer, I was able to investigate the protocol and make a working sample of its emulator.
There is no device with HU remote management around, so I have to give up with that yet.
Once again, now my emulator can work as CD-changer unit and perform its functions only.