About OpenMoko Rotate

Vasco Névoa vasco.nevoa at sapo.pt
Sat Sep 20 16:12:22 CEST 2008

I haven't looked at the code yet, but my instinctive approach would be 
to calculate the direction of the "down" vector (constant 9.8m/s2 
acceleration) and then compare that to the phone's "down" direction. It 
is the difference between these two vectors that I am referring to. Even 
if the error is great, surely it is not superior to 45 degrees (a 
quarter turn)?
Is this not the way it is done?

Fox Mulder wrote:
> This is not so easy to do. The rotation comes out of a calculation of
> the values from acceleration sensors. There are no "angle" sensors for
> this operation. So there is no way of exactly say which angle the neo
> currently has instead these are just aproximations.
> Ciao,
>      Rainer
> Vasco Névoa wrote:
>> That's very cool. I appreciate the mod. :)
>> I'm seeing something that looks like a bug (in both versions)... but I'm 
>> not sure if the accelerometers require calibration or something.
>> With the FR in vertical position, if I tilt it counter-clockwise, it 
>> takes just over 90 degrees to get 'accel-rotate' to change the 
>> orientation; but if I tilt it even less than 10 degrees clockwise after 
>> that, it reverts back to the original orientation.
>> Shouldn't the threshold be set at the midpoint angles (45, 135, 225, 315 
>> degrees)?
>> Anyway, good work to both coders, it's just what I wanted. :D
>> Maybe someone cares to extend this simple app to use some kind of sexy 
>> morph instead of the disruptive xrandr rotation? 8-)
>> Rui Miguel Silva Seabra wrote:
>>> Done. I've added a reference to it at http://wiki.openmoko.org/wiki/Rotate
>>> but my page about it is at
>>> http://blog.1407.org/2008/09/20/openmoko-rotate-now-using-libxrandr/
>>> Users of Rotate, I've patched it so it doesn't use system+xrandr but
>>> simply call directly the xrandr function using libxrandr.
>>> This means:
>>>  * quicker
>>>  * less battery consumption
>>> Best,
>>> Rui
>>> On Fri, Sep 19, 2008 at 10:13:29AM +0100, Rui Miguel Silva Seabra wrote:
>>>> Hi,
>>>> I'm preparing a patch for using xrandr api directly in Rotate instead of
>>>> system(). It's almost done but I can only code it at home time (which, for
>>>> me, starts again in about 9 hours) :)
>>>> This will be much better in terms of speed and battery life!
>>>> Best,
>>>> Rui
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