MP3 Audiotext

[RichardP1]

To see what happening you need to know quite a lot about the way that the various modules (Radio, Nav Computer, CDC and display) interact with each other.

To display the AudioText screen the CDC sends messages containing the text to the radio, the radio sends messages to the Nav Computer and the Nav computer renders the display on the monitor.

It's pretty obvious that BMW never envisaged a new BM53/54 and CDC being installed with a MK III computer, very short sighted of them.

Also, the design of the messaging system is very poor, the BM53/54 has no way of knowing if there is a MK III or MK IV computer attached.

So with the Mk III, the BM53/54 sees the messages from the CDC that contain the ID3 info, so enables the AudioText option. The Mk III understands the messages to display the AudioText option, as that uses one of the older screen display types. The messages sent to display the AudioText are sent to, and received by, your MK III computer, it just does not understand them. The BM53/54 says "go to the AudioText type screen and display these three lines of text", the MK III gets the messages and ignores them as it does not know what the AudioText screen is.

I don't know why the Select button does not work, maybe the previous commands to switch to the new (unsupported) screen have confused the Nav Computer?