[maemo-developers] Signal processing on N800

[From: nisha jain]

Hi,

Thanks for the information actually I am using wireless sensor data using
mote. It is giving the gyroscope and accelerometer data. I am very new to
DSP and I have to calculate the PSD power density spectral of 8, 10 and 20
samples of incomming data. While going through the tutorials and book I
figured that i can either take the auto correlation of signals which is
nothing but by taking fft and taking real and imaginary frquency components
magnitude. Is there direct c routine which i can invoke from my application
for maemo to calculate the PSD. I wanted it for the application running on
N800 (developed using maemo) if there is such routine for ARM please let me
know.

Thanks and Regards,
Nisha


On 4/23/08, David Huggins-Daines <dhuggins at cs.cmu.edu> wrote:
>
> On Wed, 2008-04-23 at 14:15 -0500, nisha jain wrote:
>
> > to port it to N800 later on...Please let me know if some one has
> > developed such
> > application and used fft calculation for discrete signals...
>
> If you are dealing with real-valued data (e.g. audio), you can use the
> fixed-point FFT routine in CMU Sphinx if you like.  It's not
> specifically optimized for the ARM but it's pretty fast.  Browse the
> code at:
>
>
> http://cmusphinx.svn.sourceforge.net/viewvc/cmusphinx/trunk/sphinxbase/src/libsphinxbase/fe/fe_sigproc.c?view=markup
>
> The functions you need are fe_create_twiddle() and fe_fft_real().  They
> come in 16 and 32-bit versions, based on the FIXED16 preprocessor
> symbol.  The 32-bit version is a bit confusing since it uses 20.12
> fixed-point format, so I'd recommend the 16-bit one (which is faster
> anyway).
>
> You'll have to do a bit of work to separate it from the rest of the
> front end processing, but that shouldn't be hard.
>
> Better would be to use TI's dsplib on the DSP core, but I still haven't
> gotten around to figuring that out.
>
>
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