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Subject: Re: Archos Jukebox design flaw
From: Andrew Jamieson (andrew.jamieson_at_projectlab.net)
Date: 2003-01-09


> maybe a
> USB-charged device was originally part of the design spec, and they were
> working towards that, but the feature later got dropped

Yes, this is quite possibly the case.

> (this message is
> in email, BTW, not on the list)

Whoopsy!! Wrong button. I was wondering where it had gotten too.

> What are some
> of the issues you're thinking about.

Ideally, I would like to see it made as a cable dongle, so that you plug in
your (_standard A-B_) USB cable, then plug the dongle into the device, maybe
via a short integrated cable. This way, you could take your Archos anywhere
you expect to have a computer, and just pop the small dongle into a handy
pocket for charging/USB access. This would eliminate the requirement to
take both a A-A cable and Archos plug-pack with you, as you can probably
rely on finding a standard A-B cable where-ever.

The problem with this is that it requires breaking out the USB signals from
the original cable, across the dongle board, to the integrated cable. This
is a definite problem with the USB2 signals, as it will create an impedance
discontinuity at this point (unless done on a properly manufactured PCB),
which can completely destroy the signal. However, this can be mitigated by
reducing the path for which the signals have uncontrolled impedance, and I
don't think it should be a show-stopper.

The other problem is keeping the current draw below 500mA at the 5V side.
This can probably be solved on the player by just 'tuning' the output
voltage so that even flat batteries do not draw too much current when
charging. However, the recorder uses a smarter charge circuit, and this may
not be enough ... I'll have to check.

I will bash out a schematic of what I am thinking of tonight, and post it
for comments.



Page was last modified "Jan 10 2012" The Rockbox Crew
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