linux-kernel - Re: [POWER] battery calibration parameters from sysfs

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Date:	Wed, 16 Dec 2009 00:32:18 +0100
From:	Stanislav Brabec <utx@...guin.cz>
To:	Aras Vaichas <arasv@...ellan-technology.com>
Cc:	Bill Gatliff <bgat@...lgatliff.com>, Pavel Machek <pavel@....cz>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Linus Walleij <linus.walleij@...ricsson.com>, cbou@...l.ru,
	dwmw2@...radead.org, LKML <linux-kernel@...r.kernel.org>,
	linux-embedded@...r.kernel.org,
	Brian Swetland <swetland@...gle.com>, rpurdie@...ys.net,
	lenz@...wisc.edu, Dirk@...er-online.de, arminlitzel@....de,
	Cyril Hrubis <metan@....cz>, thommycheck@...il.com,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	dbaryshkov@...il.com, omegamoon@...il.com, eric.y.miao@...il.com,
	zaurus-devel@...ts.linuxtogo.org
Subject: Re: [POWER] battery calibration parameters from sysfs

Aras Vaichas wrote:

> Yes, but in that case you might as well just purchase a coulomb
> counter with a built-in accumulator and an I2C/SPI/microwire interface
> save yourself some PCB space and cost (maybe)

Well, Pavel attempts to implement a "poor man's Coulomb counter" or at
least "poor man's Ampere meter" for devices that are not equipped with
any of it.

- We know the time.
- We know the backlight power consumption, it's dependent only on
  brightness.
- We know how much eats the HDD and how long it is on.
- We know how much eats the CPU and companion chips (it is not as
  stable, but it eats less).
- We don't know, how much USB host eats, but we know how much USB
  clients claim to eat.
- Well, and we don't know how much eats CF and SD.

=> We can guess how many Coulombs the device already consumed. If the
Coulomb counting would be inaccurate, we can at least correct voltage ->
remaining energy table using current power consumption guess.


________________________________________________________________________
Stanislav Brabec
http://www.penguin.cz/~utx/zaurus

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