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Subject: Re: AW: More aggressive Rockbox battery charging

Re: AW: More aggressive Rockbox battery charging

From: Jerry Van Baren <gerald.vanbaren_at_smiths-aerospace.com>
Date: 2005-02-11

Matthias Klumpp wrote:
> Hi Jerry and all others,

[snip]

> The test is now completed.
> CONGRATULATIONS - I guess that's it :-)))
> Don't know the original english quotation, but it should be something like
> this:
> "a short step for Jerry, but a big step for 'Rockbox-hood'...." ;-O))

Just an email to let you know I haven't been sleeping at night ;-). I am
actively working on the recharging code in powermgmt.c. I'm doing a
fairly comprehensive overhaul, factoring out duplicated code and
re-arranging things so that I understand it better. I'm putting in
improvements (hopefully :-) as I go.

Patience... hopefully after the weekend I will have something to show
the world. It will then require testing to make sure it is recharging
acceptably and to make sure I haven't broken any of the other Rockbox
platforms.

Random observations:
* I used the debug screen to observe the pre-diode battery charger
voltage. As the battery gets charged, the voltage drop across the diode
drops measurably. It isn't a huge amount, but it should be usable for a
charge current estimate if we go that route. Unfortunately, this
requires characterization before it would be usable.

* It would be nice to know what the scale factors of the A/D inputs are.
  The ones that are used are deducible (obviously). What is Vref for
the A/D? 3.3v? 5v?

* Interesting charger that works the same way as the Archos (thank you
google):
     http://www.angelfire.com/electronic/hayles/charge1.html
This does a soft-start -- that looks like a really good idea. For the
first N minutes (4), apply a low charge rate (0.2C). This would help
the problem of getting things going if the batteries are nearly
exhausted but not hurt the batteries if they are already fully charged.

* The mysterious AN0 "poorly scaled" battery input looks to me like it
is the threshold voltage at which the AJR hardware turns itself off.
When that voltage drops below 2v the music dies. This may be usable to
detect the "dangerously low" battery level more accurately. I haven't
experimented with this at all.

gvb
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Received on Fri Feb 11 14:32:38 2005


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