Freerunner games

[Al Johnson]

The wiki page outlines several things that can be done with the 
accelerometers, and several that can't. For the etch-a-sketch or marble 
rolling application the more appropriate section of the page would be:

"When hand-held, and stationary, the phone has quite accurate (better than a 
degree) knowledge of where 'down' is. 
Tilt in two directions can easily be calculated 
Roll about the 'down' axis cannot."

The paragraph quoted earlier in the thread then explains that by using the two 
accelerometers you can actually detect roll about the 'down' axis, but only 
if it is fast enough. In other words you can detect relatively gentle tilting 
for fine control of the marble, plus sharp rotation or translation if you 
want to rattle it about a bit.

There is also realistic coverage of how the accels can be used to improve the 
accuracy of GPS readings, especially in a car, while making clear that full 
inertial navigation is a nonstarter.

The source of the information looks like a combination of accelerometer 
datasheets and some basic physics. I've not checked the calculations, but 
they seem to be of the right order based on past experience with silicon 
accelerometers. Perhaps this is a case of the explanation making perfect 
sense to someone who already has experience in the subject, but not to those 
that don't. Any suggestions as to which bits need a better explanation?

On Wednesday 14 May 2008, Mo Abrahams wrote:
> That wiki page seems pretty pessimistic, making the accelerometers out
> as being all but useless. What is the source of the information?
>
> On Tue, 2008-05-13 at 16:03 -0700, Steven Kurylo wrote:
> > Are we going to be able to use the accelerometers for any of these games?
> >
> > The wiki says
> > (http://wiki.openmoko.org/wiki/Technical:Accelerometer_Fundamentals#Resul
> >ts) that "For gentle twisting and turning, the differential accelerations
> > are impossible to tell from noise."  To me that means rocking the neo
> > around for these won't work.
> >
> > On Tue, May 13, 2008 at 3:41 PM, steve <steve at openmoko.com> wrote:
> > > ya etch a sketch was one that we have talked about.
> > >  Too many ideas,
> > >
> > >
> > >
> > >
> > >
> > >  -----Original Message-----
> > >  From: community-bounces at lists.openmoko.org
> > >  [mailto:community-bounces at lists.openmoko.org] On Behalf Of Michael
> > > Shiloh Sent: Monday, May 12, 2008 4:19 PM
> > >  To: List for Openmoko community discussion
> > >  Subject: Re: Freerunner games
> > >
> > >  +1 for both of these. I can see Snake like this being quite exciting.
> > >
> > >  I will award a t-shirt for a decent implementation of either of these.
> > >  Same for the Labyrinth game.
> > >
> > >  Start coding. You'll be getting your Freerunners soon(ish)*
> > >
> > >  Michael
> > >
> > >  * for some definition of "soon"
> > >
> > >  Ron K. Jeffries wrote:
> > >  > Etch-a-sketch using accelerometers would rock
> > >  >
> > >  > the classic Snake game would also be and cool
> > >  > with these controls
> > >  >
> > >  >
> > >  > --
> > >  > Ron K. Jeffries
> > >  > http://blog.eronj.com
> > >  >