Re: [Discuss-gnuradio] GRC+USRPx file sink problem

[Marcus D. Leech]

On 08/18/2010 01:41 PM, David Evans wrote:
> Hi,
>
> GRC Setup (used with RFX and WBX cards)...
>
> USRP1 ---to---> FFT Graphical sink (shows signal spectrum as expected)
>      and  ---to---> Complex to IShort -----to----> File Sink (signals are 
> dumped 
> to disk as expected)
>
> USRP2 ---to---> FFT Graphical sink (shows signal spectrum as expected)
>      and  ---to---> Complex to IShort ----to----> File Sink (******file is 
> all 
> zeros******)
>
> Tried with 3.3.0 and git 3.3.1, and on three different installations/USRPs. 
> Basically zero output with USRP2.
> USRP2 works fine with python scripts eg, usrp2_fft.py with --output-shorts.
>
> Any ideas please?
>
> Dave
>
>   
My guess is that with USRP2, samples are scaled -1.0 to 1.0.  Which
means that a straight conversion to
  a short integer is going to yield zero most of the time.  Try putting
a multiplier block in front of your
  file sink--maybe scale those -1.0 to +1.0 to +/- 32767.




-- 
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org