[USRP-users] E310 Rx Timeout with higher sampling rates

Philip Balister philip at opensdr.com
Thu Apr 30 17:57:55 EDT 2015


On 04/30/2015 04:24 PM, Marcus D. Leech via USRP-users wrote:
> On 04/30/2015 03:38 PM, Voss, Nathan J wrote:
>> I am running in native mode.
>>
>> Running the 'rx_samples_to_file' application, I am able to get up to
>> about 10Msps on the E310 before overflow issues arise. Definitely
>> better than what I'm seeing in my own application, although I'm still
>> surprised that it is capping out at only 10MHz when the advertised
>> (analog) bandwidth is 56MHz. I'm also not seeing any 'Timeout' error
>> codes from the sample application.
>>
>> For the record, my command line is:
>>> rx_samples_to_file --args="master_clock_rate=56e6" --ant "RX2" --freq
>>> 315000000 --null --spb 512 --gain 25.0 --progress --type float
>> I am running the stock image that comes shipped with the E310. I have
>> seen previous posts regarding updating the SD image to the 'Dizzy
>> Beta' image. Would that potentially have anything to do with this
>> issue? I've double checked my code for any obvious problems, and have
>> confirmed that my 'rx_metadata' is set with no time_spec (which could
>> cause delay before samples start) and also made sure that the stream
>> is successfully started in continuous mode before I call recv().
>>
>> Thanks again for your help.
>>
> The "Dizzy" images may have marginally better performance, not sure what
> the differences are.


The current test image has uhd-3.8.3. That has a couple of important bug
fixes for the E310.

http://files.ettus.com/e3xx_images/beta/dizzy-test/

You need to write the image to an 8 GB card.

bmaptool can save you some time writing the image to the card:

http://gnuradio.org/redmine/projects/gnuradio/wiki/Copy_an_image_file_to_the_SD_card

Philip

> 
> But getting 10Msps through the ARM CPU is, to be honest,
> near-miraculous.     The E310 has a dual-core ARM cpu, clocked at 700MHz
> or so.  If you
>   thought of it as somewhere around what a ho-hum desktop x86 machine
> was 3-4 years ago, that would be about right.
> 
> You'll have to optimize your own application, use standard profiling
> tools to find out where your hotspots are.
> 
> But also, it is intended that high-rate processing on the E310 happen on
> the FPGA, not on the Zynq CPU cores.   That's why E310 has a larger
>   FPGA, and supports RFNoC.   With current technology, there's no way a
> couple of ARM CPUs are going to be able to "keep up" at 50Msps, even
>   for relatively-trivial stuff.   Even on current-desktop hardware, just
> recording samples to an SSD at 50Msps is *challenging*.
> 
> 
> 
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