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Subject: Re: BMW IBUS <-> Archos Jukebox (as CD Changer)

Re: BMW IBUS <-> Archos Jukebox (as CD Changer)

From: jobarjo <>
Date: Mon, 15 Mar 2004 13:23:11 +0100

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" <>
To: <>
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
> 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
> 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
> 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
> _______________________________________________

Received on 2004-03-15

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