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Subject: Re: Archos <-> BMW IBUS
From: [IDC]Dragon (idc-dragon_at_gmx.de)
Date: 2004-03-02


> I'm trying to interface the Archos player with a BMW headunit that uses
> IBUS
> (a serial line at 9600bps, even parity, one stop bit, pulled up to +12V).
> The frames have the following format:
>
>
> sender, length, destination, message body, checksum
>
>
> the length includes the destination, message body and checksum bytes. The
> checksum is similar to M-BUS (an xor of all bytes).
>
>
> As I understand from Jörg experiences, he connected the Archos directly to
> the MBUS and all went fine. I'm afraid that doing the same might damage
> either the archos or, even worse, a component from my car connected to the
> IBUS.
>
>
> I know very little about low level electronics (I really hate discrete
> components!) but I wanted a converter circuit from the TTL levels of the
> Archos to the IBUS signals. Can someone help me on this? Can a simple
> voltage divider work in this case to drop the line from 12 to around 4 V?
> I
> really know very little about the subject :(
>
>
> I modified Jörg's alpine_cdc.c code to talk at 9600bps 8e1 and all that is
> preventing me to test the code is the damn interface... I already have
> done
> a few experiences controlling 6 fixed playlists and the mpeg/playlist code
> is now working well. In fact it wasn't too hard. I was having trouble
> stoping the mpeg playback because I was trying to do it by capturing the
> STOP button on the remote control (by calling button_get()). As soon as I
> changed this to another button on the remote control everything was fine.
> Beats me completely why it doesn't work with the STOP button but I suspect
> it is being captured at a previous point in the code and some processing
> was
> colliding with my code.
>
>
> So, in resume, I have a ibus_main() function being called from app_main(),
> just before browse_root(). When a key is pressed in the archos the IBUS
> CDC
> emulator exits and the jukebox returns to its normal operation. This is
> just
> an easy way to have both things running so that I can easily use it in the
> car and at home. I have all the serial code ready to be tested and when it
> works I will be able to build the CDC emulator part (this is probably the
> easier part as the protocol is quite simple)...
>
>
> So, I hope someone can help me on this topic...
>
>
> Thanks to the group.
>
> Fernando Birra
>
>
> _______________________________________________
> http://cool.haxx.se/mailman/listinfo/rockbox
>

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