Hi!

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to introduce coefficients for temperature and discharge rate?

What do you mean? Nothing like that is used in current driver why do
we need to add it?

Well, conversion between Li-ion's voltage and state of charge at 0
current is well known:

We can?t measure at 0 current since the OMAP is driven from battery
and charger and may also draw some mA?

Yes, but you know how many mA you are taking just now. So if you knew
the internal resistance, you could compute the voltage at 0
current. (And it should also work during charging, as long as you know
how much current is going in.)

As far as I understand the twl4030 charger and MADC it is not possible to
separate these values. It is only reporting the inflow from charger to
battery + system. So you don?t know how many mA are supplying the system
and how many mA are left over for charging.

You can only assume how much the system is drawing while running (something
between 50 and 600 mA but this depends on system activities, power state
of peripherald and e.g. backlight being switched on).

I think your basic assumption that we know any time how many mA the system
is taking is not given.

So.. you won't be able to get exact value while charging, but you
get one while discharging, which is what really matters...?

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Yes, and that coefficient should be internal battery resistance ;-).

But where do you know this value from to write it into a DT file?
Usually you can?t measure it easily and for some batteries you don?t have
a data sheet.

Contrary, the calibration curves can easily be measured on the device
(assuming that the charge level decreases/increases linearly over time
between Full and Empty).

If you can copy it from the data sheet, that's the easiest option. If
not, you should be able to easily compute it from the charge/discharge
curves or from measured voltage at different loads.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html