Originally Posted by bmviz
thanks for your correction Jspira, I'm maybe confused but I hope you can help us with your knowledge
In reference to non Idrive systems, the CD drive build in the "Radio" (I'm not sure what exactly it called in BMW world) and not connected directly to the MOST bus via fiber.
Additionally, the problem is not the "MOST" as much as the way that BMW implemented it in close system type. That mean that the "master" computer that controls the MOST bus have to be programed to all of the active devices on the bus to let them communicate on the MOST bus. That is the main issue that if you adding a new device (like alarm or Ipod interface for example) you have to go to the dealer to "reprogram" the car.
Most of other cars manufactures using "open" protocol that have the capability to discover new devices (kind of plug-and-play) connected to MOST bus. Examples are VW, Audi, Saab, Citroen, Reno, etc...
I know that USB interface is available for some of those car already and I think that you are correct in the assumption that they are probably emulating CD changers and probably connected directly to the head unit and not to the Most bus (because of the issues that you mention earlier).
Sorry for long post, but I know that you have very technical posts and it looks that you have experience and access to BMW technical documentation.
Please advice if I got this wrong again
This is a tough question so letīs try to go thru this.
First, you are right to note that BMW has adopted MOST in a relatively closed fashion although it is still an open standard. I have not been able to get a direct answer as to why they did this but the indirect answer was to ensure the integrity of what is connected. It is a valid point to some extent.
The CD drive is attached to the MID (multi information display) in non iDrive cars. The MID sits on the bus. I donīt recall where the radio (i.e. receiver) is but sometimes (based on past BMWs) itīs been in a module in the trunk or itīs been built into the CD drive (E39 5er with MID without DSP). It might be in the MID module but what everyone thinks is a ,,head unit`` is the MID.
Regarding CD changer emulation. In most cars (sorry for the pun), the cd changer is attached directly to the MOST fiber optic bus. I have not seen the drawings for the USB in the new BMW so I donīt know how this connects but it is definitely NOT using the CD changer connection and therefore doesnīt have to emulate the changer.
In fact, BMW is going this route so they donīt have the limitations of changer emulation. My guess is that the USB module does connect directly to the bus or to a module that interprets the information.
Iīll find out more and post.
Hope this helps.