Rockbox mail archive
Subject: Re: BMW IBUS <-> Archos Jukebox (as CD Changer)
From: [IDC]Dragon (idc-dragon_at_gmx.de)
> >I have used the same transistor when I started my hookup with a level
> >shifter. It worked, and later I found it's not needed.
> In my case if I connect the archos directly to the bus I read around 8V at
> the pin/bus when the archos forces the bus to low state.
Uh, oh. It should collapse to about 4V when you connect to an open drain /
open collector bus. If you get more, either some bus pullup is way to strong
(impedance too low), or something is _driving_ the bus high (then it wouldn't
be open drain). Very harmful to your poor remote input!
If you really have 8V on the remote pin, the RX pin of your CPU is in
> I tried changing and it still did't work. Also, doesn't the fact that the
> direct connection (without any level shifter) also has the problem of not
> being capable of driving the bus low suggests that the problem are not the
Yes, definitely. Is your connector OK? Gnd is the outermost pin, RX is the
second. Camcorder TV out cables I've seen have these pins in reverse order.
> >>Another explaination could be that the pullup is very strong, so the
> >>fails to pull it low. How much current do you measure when you short
> >>to ground (or bus to ground)? The SH is specified to sink max. 10 mA.
> I'm not sure if I understood it (I really know very little about
> electronics). Do you want me to measure the current that through to the
> source or drain pins when either the source or bus is short to ground? I
> tried but I always got 0 mA, I'm sure I made some mistake...
> Can I connect one test lead of the multimeter to the ground and the other
> one to the source pin to measure it?
Use your multimeter in maybe 200 mA range setting to short the bus to
ground. For amp measurements, most meters require to move the positive plug. Don't
measure in parallel to a short you already made (you don't need one), because
then the current travels there and not through your meter.
Let's hope for the best.
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Page was last modified "Jan 10 2012" The Rockbox Crew