[USRP-users] E310: signal processing possible on the FPGA

Philip Balister philip at opensdr.com
Tue Oct 20 13:36:21 EDT 2015


On 10/20/2015 09:51 AM, Martin Braun via USRP-users wrote:
> On 19.10.2015 16:41, Chris Stankevitz via USRP-users wrote:
>> I would like to run a filter which essentially averages the power of
>> the signal over the past x samples.  If and when a threshold is
>> exceeded, I would like the ARM CPU to be given the raw samples for
>> subsequent high-level processing.
>>
>> I know how to perform this process entirely on the ARM CPU: use the
>> UHD library to grab the raw samples and perform the power-calculating
>> filter on the ARM CPU.  But I'm not sure the ARM CPU will be able to
>> keep up as I increase the sample rate (ideally to 10 MHz).
>>
>> Is it possible for the USRP E310 to perform this kind of signal
>> processing on "the FPGA" instead of on "the ARM"?  If so, by what
>> mechanism will the results of this processing (the average power in
>> my example) be made available to the UHD client application?  Is it
>> possible that, using UHD, I am delivered 3 scalars for each sample:
>> real, imaginary, and the result of some filter e.g. avg power?
>>
>> I've been assuming that this processing must occur on the ARM CPU
>> until a few minutes ago a colleague wondered aloud "I think the E310
>> can run some flow graphs on the FPGA itself at the full sample
>> rate".
> 
> Yes, this is true. We are working on a framework called 'RFNoC' which
> will let you do this with a minimum of hassle (some FPGA work is still
> required, though). See also
> http://www.ettus.com/sdr-software/detail/rf-network-on-chip.

There are test images with rfnoc support at:

http://files.ettus.com/e3xx_images/alpha/fido-rfnoc-test/

You do need to run "uhd_images_downloader" to get the correct fpga images.

Philip

> 
> RFNoC is not yet released as part of an official UHD release, but it's
> already quite stable and many people have built applications using it.
> You'll find a small getting started guide here:
> https://github.com/EttusResearch/uhd/wiki, and there's also some videos
> on RFNoC here:
> http://www.ettus.com/blog/2015/06/rfnoc-for-high-performance-sdr or as
> part of last year's GNU Radio conference:
> http://www.trondeau.com/grcon15-presentations/ (look for RFNoC).
> 
> Cheers,
> Martin
> 
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