[Gta04-owner] Making sense of the sensors.

Michele Brocco ssj2micvm at gmail.com
Thu Aug 9 23:07:23 CEST 2012


Is the needle going crazy or is it constantly showing in the same
direction if you don't move your device?


On 8/9/12, Benjamin Deering <ben_deering at swissmail.org> wrote:
>
> I played a bit with valacompass on GTA04.  Libsensmon would need a
> BMA150 module for tilt compensation to work, but I commented out the
> accelerometer code in my build.
>
> The hmc5843 driver for the latest SHR kernel has the sysfs files in a
> different place.
>
> I changed .Sensmon/config to include:
> [Hmc5843Source]
> device=/sys/bus/i2c/devices/2-001e/iio:device0
>
> The sysfs file 'rate' seems to have changed to sampling_frequency.
>
> X,Y,and Z values come from separate files.  I'm not a vala programmer,
> but I can send what I did to get them.
>
> I had to adjust in_magn_range to get the Y axis to show anything but
> -4096.0
>
> I don't know how important the tilt compensation is, but with all my
> changes the needle in valacompass does not point north.  The direction
> it points seems to change when I rotate the phone, but it is very
> noisy.  I think there is some interference from the speaker magnets as I
> was able to get a reading on the Y axis without adjusting the range if I
> brought a magnet near the phone.  I have Slyon's 3d printed speaker box
> and 2 speakers, maybe those with a single speaker will have different
> results.
>
> Ben
>
> On 08/04/2012 02:10 PM, Michele Brocco wrote:
>> On 8/4/12, NeilBrown<neilb at suse.de>  wrote:
>>> The compass seems to have a strong bias on all axes. Presumably some
>>> magnet
>>> in the GTA04 (speaker?) needs to be compensated for.  Has anyone played
>>> with
>>> this at all?  Figured out how to calibrate, then how to convert the 3
>>> numbers
>>> into  a compass direction?
>> hi neil,
>>
>> I wrote a proof of concept user space compass application for the
>> navigation board (http://wiki.openmoko.org/wiki/ValaCompass). you can
>> take a look at the source code if you want. i wanted to update the
>> application once the kernel in shr will support this sensor and the
>> accelerometers. but currently I am very busy and could not chek if
>> everything is there already.
>>
>> regards,
>>
>> Michele
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>
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