Hi Nikita, uhd_fft uses a WX sink. It does its own FFT calculations. They are not meant to be used elsewhere. I recommend using a FFT block and then format the output according to your needs.
Happy hacking Johannes On Wed, Dec 18, 2013 at 8:30 PM, Nikita Sharakhov <sha...@vt.edu> wrote: > Hello Johannes, > > > > Thanks for giving me a solution to explore. Also, would modifying > uhd_fft.py (to output a text file rather than displaying a GUI) be a good > way to accomplish my goal? Has anyone done that before? > > > > Regards, > > > > Nikita > > > > > > > > *From:* Johannes Demel [mailto:johannes.de...@ettus.com] > *Sent:* Tuesday, December 17, 2013 5:26 PM > > *To:* Nikita Sharakhov > *Cc:* discuss-gnuradio@gnu.org > *Subject:* Re: [Discuss-gnuradio] Spectrum Sensing > > > > Hi Nikita, > > so basically what you want is a couple of calculated FFTs per second. > These are then sent to the web service and delivered to who ever connects > to it. > > Let's assume every USRP has its own flowgraph. Then The thing to do is, > receive samples, convert them to a vector with the size of your FFT, use a > 'Keep one in N' block to decimate the number of FFTs per second and feed > the output to a FFT block. Then pass your results around as you like. > > Happy hacking > > Johannes > > > > On Tue, Dec 17, 2013 at 11:26 AM, Nikita Sharakhov <sha...@vt.edu> wrote: > > Hi Johannes, > > > > Here are some more details. I am building a web service, which returns > spectrum data (the amount of energy at different frequencies) for a USRP, > like so: > > > > > http://128.173.221.40/WebServices/SpectrumAPIfineGrain.php?node=49&frq=2000000000 > > > > The script behind this data service calls a python program to calculate > the spectrum and write the results to a text file. Here is my goal: I > would like to find an alternative to the python program. > > > > This data is visualized in a web application: > > > > http://filebox.vt.edu/users/sharni/Radio/new.html > > > > clicking on a node visualizes the spectrum for the USRP. The RAND button > toggles between fake and real data. Currently the data is not accurate. > > > > Thanks, > > > > Nikita > > > > > > *From:* Johannes Demel [mailto:johannes.de...@ettus.com] > *Sent:* Tuesday, December 17, 2013 12:30 PM > *To:* Nikita Sharakhov > *Cc:* discuss-gnuradio@gnu.org > > > *Subject:* Re: [Discuss-gnuradio] Spectrum Sensing > > > > Hi Nikita, > > In order to answer your question we need more information on what you want > to do exactly. gr-fosphor takes all unprocessed samples and does everything > on the GPU. Calculating spectrum, graphical output etc. As far as I know > there isn't a way to get the samples back from the GPU. > > Cheers > > Johannes > > > > On Mon, Dec 16, 2013 at 8:12 PM, Nikita Sharakhov <sha...@vt.edu> wrote: > > Hi Johannes, > > > > Thanks for the answer! I am building my own web-based GUI, so I just need > a script that just writes the spectrum data to a text file or to standard > command-line output. Is that possible with gr-fosphor? Is there any other > software that I should look at? > > > > Best regards, > > > > Nikita > > > > *From:* Johannes Demel [mailto:johannes.de...@ettus.com] > *Sent:* Monday, December 16, 2013 10:58 PM > *To:* Nikita Sharakhov > *Subject:* Re: [Discuss-gnuradio] Spectrum Sensing > > > > Hi Nikita, > > 'uhd_fft' is only a graphical frontend for your flowgraph. It contains a > WX FFT Sink and some information about your setup. The WX FFT Sink itself > seems to be so fast because it only calculates about 10 FFTs per second. > All the other input samples are simply dropped. If you want to have a real > real-time GUI take a look at gr-fosphor. > > If a few snapshots of the spectrum per second are sufficient for you, > think about a keeping only a tiny fraction of your input samples. This will > speed things up. On the other hand, if you want to calculate a FFT for all > samples, look at the FFT block. BTW: the output of the FFT block would be > the 'raw samples' you were asking for. > > Happy hacking > > Johannes > > > > On Mon, Dec 16, 2013 at 8:03 AM, Nikita Sharakhov <sha...@vt.edu> wrote: > > I would like to do spectrum sensing with GNU radio. Is there a good way to > get the raw output from uhd_fft.py (the value for each frequency)? I would > like to do this programatically (with code), rather than through a GUI. > > I have tried doing spectrum sensing with usrp_spectrum_sense.py, and this > script has questionable accuracy and seems to be much slower than > uhd_fft.py. > > Thanks! > > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > > > >
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