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Subject: Re: BMW IBUS <-> Archos Jukebox (as CD Changer)
From: jobarjo (jobarjo78_at_yahoo.fr)
Date: 2004-03-15


Your RS232 adapter is certainly not open drain, so when it drives a 1, your
archos cannot drive a 0

----- Original Message -----
From: "Fernando Birra" <fpb_at_di.fct.unl.pt>
To: <rockbox_at_cool.haxx.se>
Sent: Friday, March 12, 2004 9:31 AM
Subject: BMW IBUS <-> Archos Jukebox (as CD Changer)

> Hi,
>
> I tried to interface the archos to the BMW IBUS (serial line pulled up to
> 12V and brounght down to 0 by the talker) but only partailly managed to do
> it. I have an RS232 adaptor to talk to the bus with a PC and I used it to
> debug the trasmit routines. So, I can send and receive packets to the bus
> with the archos with this setup:
>
> PC <-> RS232-IBUS adaptor <-> IBUS wire <-> MOSFET Level Shifter (3V-12V)
> <-> Archos
>
> The connections on the MOSFET are:
>
> Source - Archos Remote Control Pin
> Gate - 3V Power Suppy
> Drain - BMW IBUS
>
> However, when I plug the archos with the mosfet level shifter to the car
bus
> I can receive (sometimes with errors) but I cannot send. I managed to
> identify the problem but I don't know the solution...
>
> The trouble is that when I connect the archos to the car bus with the
mosfet
> level shifter (I used a BS170) when the archos forces the bus low it can
> only bring it to around 1.2 Volts and when I look to the drain pin I still
> see around 12V. If I short circuit the ground with the source pin then I
can
> bring the drain pin (connected to the car BUS) to around 0V.
>
> I really don't know how to solve this and it would be great if you could
> help me. Would it help connecting to a different MOSFET with a lower Vgs
> threshold value?
>
>
> Thanks
> Fernando Birra
>
>
> _______________________________________________
> http://cool.haxx.se/mailman/listinfo/rockbox

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