# g-sensor calibration problem

John Lee john_lee at openmoko.com
Fri Jun 20 11:40:40 CEST 2008

```On Fri, Jun 20, 2008 at 11:32:39AM +0200, Carl-Daniel Hailfinger wrote:
> Hi,
>
> On 20.06.2008 11:02, John Lee wrote:
> > Hi,
> >
> > If I use the enclosed python code to test g-sensor on gta02 (read
> > /dev/input/event3) while holding the neo vertically, normally the
> > result looks like this:
> >
> > x = -72, y = -990, t = 1.976891 pi
> > x = -72, y = -990, t = 1.976891 pi
> > x = -54, y = -990, t = 1.982655 pi <=======================
> > x = -72, y = -990, t = 1.976891 pi
> > x = -72, y = -990, t = 1.976891 pi
> >
> > It's quite reasonable.  However,
> >
> > * sometimes after booting
> > * always after resume (apm -s)
> >
> > the result will look like this:
> >
> > x = 1620, y = -36, t = 0.492928 pi
> > x = 1620, y = -18, t = 0.496463 pi <=======================
> > x = 1620, y = -36, t = 0.492928 pi
> > x = 1620, y = -36, t = 0.492928 pi
> > x = 1620, y = -36, t = 0.492928 pi
> >
> > I wonder what's the cause?  Any more information I could provide?
> >
>
> look similar to the touchscreen deviations. John, can you give us a
> longer line of measurements with the neo lying flat on a table?
> Andy?

flat on table

normal result
x = 36, y = -18, t = 0.352416 pi
x = 36, y = -36, t = 0.250000 pi
x = 36, y = -36, t = 0.250000 pi
x = 36, y = -18, t = 0.352416 pi
x = 36, y = -36, t = 0.250000 pi
x = 18, y = -36, t = 0.147584 pi
x = 36, y = -36, t = 0.250000 pi
x = 36, y = -18, t = 0.352416 pi
x = 36, y = -18, t = 0.352416 pi
x = 36, y = -36, t = 0.250000 pi

abnormal:
x = 1620, y = -36, t = 0.492928 pi
x = 1620, y = -36, t = 0.492928 pi
x = 1620, y = -36, t = 0.492928 pi
x = 1620, y = -36, t = 0.492928 pi
x = 1620, y = -18, t = 0.496463 pi
x = 1620, y = -18, t = 0.496463 pi
x = 1620, y = -18, t = 0.496463 pi
x = 1620, y = -36, t = 0.492928 pi
x = 1620, y = -18, t = 0.496463 pi
x = 1620, y = -36, t = 0.492928 pi

- John

```