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Subject: Re: new thread about remote control with display
From: Andreas Zwirtes (zwirtes_at_gmx.de)
Date: 2002-10-09


Just want to write about that recharging issue first, next will be protocol.

Is there any possibility to charge / supply a circuit that already runs
on 3.2V from a good battery with a processor port pin that delivers only
approx 3V? Yes, you can use a switching power supply in current mode,
but that'll be very difficult and maybe also draw all the power it
delivers by itself. I know, the processor in the Jukebox is powered by a
3.3V regulator, but 3V would be the maximum voltage (let's say with 1mA
load) that you'll see on the remote.I've recorded the discharge curve
for a CR2032 long ago, maybe I'll find a copy in my office.

I did some testing on that and drove about 1mA (Square/440Hz) over the
GND-line of my amplifier cable to the rockbox. You can hear that very
good. Setup was: Battery ground <-- Plug GND <-- Cable GND <-- Amplifier
GND <-- Current source. (current from right to left ;). The current
source will be our remote via the processor supply doing lots of
communication and power switching. Maybe wrong test setup... Any ideas?

I totally agree with you, that we should keep this in mind, because a
long battery life will be appreciated by everybody. If we are able to
work with one batt for about a year in the future (maybe direct driven
LCD), that should be enough reason not to compromise the communication
or audio quality. (or even endanger our holy processor). I'd be very
pleased, if someboy come up with a solution to the mentioned problems,
because 400hrs isn't that much....

Andreas
[radhard]



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