[Gta04-owner] Making sense of the sensors.

NeilBrown neilb at suse.de
Fri Aug 10 00:15:41 CEST 2012

On Thu, 9 Aug 2012 23:23:27 +0200 Belisko Marek <marek.belisko at gmail.com>

> On Thu, Aug 9, 2012 at 11:13 PM, Benjamin Deering
> <ben_deering at swissmail.org> wrote:
> >
> > It is going crazy.  I watched the 3 axis in sensmon.  X and Y are reasonable
> > if I adjust the range, but Z sends random looking garbage.  Even moving a
> > powerful magnet close around the phone makes no noticeable change.
> Maybe there is some bug in driver. I've remember when working on
> driver I've got -4096 for Z value
> most of the time which means invalid but cannot figure out why.
> Anybody else can share test results?

I get -4096 on my X axis unless I adjust the sensitivity.   It simply means
that the sensor has saturated - the magnetic field is too strong.

I've been thinking about adding an 'auto' mode to the sensitivity so that it
will adjust downwards whenever it gets -4096, then scale the measured results
up to compensate.

I haven't tried valacompass, but just watching the numbers change as I move
the phone around seems to show the right sort of pattern in the three axes.
I think I want to collect a set of numbers and try graphing them just to be
sure though.

I tried spinning around slowly and X would have a maxima in the opposite
direction to its minima, however I don't think Y was at its midpoint then,
which seems strange.  Drawing graphs should help take the guess work out.


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