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Re: [Discuss-gnuradio] USRP Under Flow

From: Philip Balister
Subject: Re: [Discuss-gnuradio] USRP Under Flow
Date: Thu, 18 Mar 2010 07:27:23 -0400
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On 03/18/2010 07:21 AM, halidziya yerebakan wrote:
Any way , my cpu is not very busy when it is working problem is some where
else acording to me ,
I don't know how to use blocks in python but maybe we can create a block
between audio device and output device that converts 32 khz to 48 khz

When it underflows, I suspect there is idle time while the system recovers. That drops the apparent CPU usage. Most likely the flowgraph is waiting on the IO to notify you the underflow occurred.

         audio_decimation = 10
         audio_rate = demod_rate / audio_decimation  # 32 kHz

The fm demod already has a sample rate conversion in it, but it only supports decimation, not resampling to an arbitrary rate. If you use an external resampler to get the 32 kHz back to 48 kHz, you have two different FIR filters running, when you really only need one.


On Thu, Mar 18, 2010 at 1:08 PM, Philip Balister<address@hidden>wrote:

On 03/17/2010 03:15 PM, Jeff Brower wrote:


  My beagle board is clone and it is working in 200MHZ , but when I run the
it doesn't consumes to much CPU time

A Beagle board clone?  The Beagle board already costs less than its
component BOM.
Did you alter the design in some way?

There is the EBV clone in Europe and possibly ones from India and China. It
is easy to clone :) I don't think the Beagle sells under material cost, but
I suspect the margin is not a sustainable business model.

Also, why only 200 MHz?  That's way slow... what is the reason?

That sounds wrong. Stock Beagles run at 500 MHz and can be turned up to 600
MHz. Newer Beagles run up to 720Mhz

Yes, using the DSP is very interesting. Approaches range in complexity from
wrapping a call to do the processing in the DSP from the existing gnuradio
block structure to integrating the DSP into the gnuradio block scheduler.



  On Tue, Mar 16, 2010 at 9:59 PM, Jeff Brower<address@hidden>


      >   On 03/16/2010 06:51 AM, halidziya yerebakan wrote:
      >>   Hi all;
      >>   ?  ?  ?  ?  Thanks to Mr. Balister I run USRP on BeagleBoard (

      >>   http://www.opensdr.com/node/17) . But it doesn't give any sound
when I
      >>   to listen FM radio. I think there is some mismatch in sampling
      or data
      >>   format. I read other mail list archives but they didn't solve my
      >>   Here is my console :
      >>   address@hidden:/usr/share/gnuradio/examples/usrp#
      >>   Using RX d'board A: Basic Rx
      >>>>>   gr_fir_fff: using cortex_a8
      >>   Freq: 100.1M ? Volume:0.100000 ? Setting:FREQ
      >>   OK


      >>   (No Sound Here goes like this )
      >   Run oprofile, find the code that takes all the time, optimize
      >   NEON, repeat :)
      >   The sample rate conversions will be the CPU hogs for this
waveform. It
      >   looks like you are using an optimized fir filter already, but
      >   through the sample rates at each step. It is possible the audio
out is
      >   doing another rate conversion. Also, the gnuradio block may
create a
      >   very long fir filter, you can adjust the filter design settings
      >   reduce the number of taps.
      >   It will work, but you do not have many GHz of cpu to cover up
      >   in-efficient design decisions :)

      At what rates are the OMAP 3530 cores running on the Beagle board? ?
      web page says "up to" 600 MHz for the ARM A8
      and up to 430 MHz for the C64x+ core. ? Sometimes TI eval/dsk boards
      don't always run at max rate...

      Also, do you know if anyone has done work to port GNU radio
      over to the C64x+ core? ? For example you mention
      sample rate conversion, that would be very suitable to offload onto


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