[USRP-users] problem with USRP example on X310 with CBX-120

Marcus D. Leech mleech at ripnet.com
Wed Oct 29 18:48:24 EDT 2014


On 10/29/2014 06:32 PM, Michael West via USRP-users wrote:
> Hi Jim,
>
> I set up an X310 and CBX-120 with a loopback cable between TX/RX and 
> RX2 and ran the same command as in your test.log file (with a 
> reduction of the sample rate to 10 Msps and not using the CAL 
> antenna).  I did add the argument "--type float" to get fc32 samples 
> in the file so I could use my existing GRC flowgraph to plot the 
> data.  I saw no issues in the resulting data (see the attached 
> screenshot of the FFT and scope plots).  I then set up a quick GRC 
> flowgraph with the same settings and FFT and Scope sinks connected to 
> the USRP Source.  I saw no issues at all (see the attached 
> screenshot).  The fact that you see no issues when using external 
> instruments and the same command works just fine for me suggests that 
> there is some problem with how the data is being processed to 
> generated the graphs.  You could try switching to the float type and 
> see if your results get any better.
>
> By the way, I also did a run with the RX antenna set to CAL and I 
> noticed that the signal strength was about 30-35 dB lower (as expected).
>
> Regards,
> Michael
>
I just did the same thing, after running the uhd_cal routines, and got 
very-clean FFT results, using 0dB gain settings on both TX and RX, and
   with antennae set to TX/RX and RX2 respectively (just relying on 
leakage).

This is with the latest UHD, but that shouldn't matter.


> On Wed, Oct 29, 2014 at 12:29 PM, Jim Hunziker 
> <jhunziker at bcisensors.com <mailto:jhunziker at bcisensors.com>> wrote:
>
>     OK, as Frank said in a separate email, the cal patch didn't seem
>     to fix our problems. The only thing we're using to control the
>     X310 (and CBX-120) is txrx_loopback_to_file.
>
>     Attached is a zip file with a log of what we're doing and some
>     images to go along with it. Our X310 isn't hooked up to anything,
>     and we're using CAL as the receive antenna. (We've tried this same
>     test with a loopback cable and RX2, but it doesn't make a difference.)
>
>     The fft.png image is an FFT of the received data, zoomed to
>     baseband and the 1 MHz signal that was up- and down-converted to
>     5.6 GHz. You can see the 1 MHz signal at the correct frequency.
>     The other images are showing the quality (or lack thereof) of the
>     received signal. Not long after the capture starts, the 1 MHz
>     signal is no longer detectable.
>
>     In the test.log file, you can see how we're running
>     txrx_loopback_to_file and what gets spit out as it runs. You can
>     also see the commands that I'm using (in Python, with NumPy,
>     though the commands are nearly the same as their MATLAB
>     equivalents) to generate the images.
>
>     The problem does not seem to occur (or at least not as badly) when
>     we capture the transmitted data with external test equipment. It
>     also doesn't seem to occur when we capture a signal from a signal
>     generator with the X310. All tests, even these last two, were done
>     using txrx_loopback_to_file. So our best guess is that something
>     weird is happening inside the X310 when it is being used to do a
>     full duplex TX/RX.
>
>     If you like, I can also provide usrp_samples.dat.
>
>     -- 
>     Jim Hunziker
>     BCI Systems and Software Engineering
>     jhunziker at bcisensors.com <mailto:jhunziker at bcisensors.com>
>
>     On Mon, Oct 27, 2014 at 4:05 PM, Jim Hunziker
>     <jhunziker at bcisensors.com <mailto:jhunziker at bcisensors.com>> wrote:
>
>         I found the problem. I had to run dos2unix on the patch first.
>         I'll get back to you on how it affects our tests. Thanks!
>
>
>         -- 
>         Jim Hunziker
>         BCI Systems and Software Engineering
>         jhunziker at bcisensors.com <mailto:jhunziker at bcisensors.com>
>
>         On Mon, Oct 27, 2014 at 1:32 PM, Michael West
>         <michael.west at ettus.com <mailto:michael.west at ettus.com>> wrote:
>
>             The patch should work for any version of UHD from 3.7.0
>             forward.
>
>             Michael
>
>             On Mon, Oct 27, 2014 at 7:48 AM, Jim Hunziker
>             <jhunziker at bcisensors.com
>             <mailto:jhunziker at bcisensors.com>> wrote:
>
>                 Thanks. It looks like this patch isn't against 3.7.3.
>                 We're not running against the master branch right now.
>                 Is this patch intended for 3.8-rc?
>
>
>                 -- 
>                 Jim Hunziker
>                 BCI Systems and Software Engineering
>                 jhunziker at bcisensors.com <mailto:jhunziker at bcisensors.com>
>
>                 On Fri, Oct 24, 2014 at 5:55 PM, Michael West
>                 <michael.west at ettus.com
>                 <mailto:michael.west at ettus.com>> wrote:
>
>                     Hi Jim,
>
>                     An experimental UHD patch was sent to your
>                     colleague to address the calibration issue. 
>                     Please let me know if you need the patch sent to
>                     you directly and I will get it to you.
>
>                     Best regards,
>                     Michael
>
>                     On Thu, Oct 23, 2014 at 10:40 AM, Jim Hunziker via
>                     USRP-users <usrp-users at lists.ettus.com
>                     <mailto:usrp-users at lists.ettus.com>> wrote:
>
>                         Marcus Leech responded to me off-list that I
>                         was using gain settings that were too low.
>                         Setting them to 10 greatly improved my signal,
>                         though there's still a carrier component
>                         that's bigger than my signal and not getting
>                         removed. A colleague tells me he's working
>                         with Ettus regarding this problem.
>
>
>                         -- 
>                         Jim Hunziker
>                         BCI Systems and Software Engineering
>                         jhunziker at bcisensors.com
>                         <mailto:jhunziker at bcisensors.com>
>
>                         On Wed, Oct 22, 2014 at 4:42 PM, Jim Hunziker
>                         <jhunziker at bcisensors.com
>                         <mailto:jhunziker at bcisensors.com>> wrote:
>
>                             It looks like some of my problem was
>                             plotting abs(sig_c) rather than
>                             real(sig_c), but the signal still doesn't
>                             look great.
>
>
>                             -- 
>                             Jim Hunziker
>                             BCI Systems and Software Engineering
>                             jhunziker at bcisensors.com
>                             <mailto:jhunziker at bcisensors.com>
>
>                             On Wed, Oct 22, 2014 at 12:15 PM, Jim
>                             Hunziker <jhunziker at bcisensors.com
>                             <mailto:jhunziker at bcisensors.com>> wrote:
>
>                                 Hi. I have an X310 with a CBX-120 and
>                                 a GPSDO, and I'm running the
>                                 txrx_loopback_to_file example with UHD
>                                 version 3.7.3 like this:
>
>                                 ./txrx_loopback_to_file --tx-args
>                                 addr=10.10.10.90 --nsamps=250000
>                                 --tx-rate 2500000 --rx-rate 2500000
>                                 --tx-freq 56000000
>                                 00 --rx-freq 5600000000 --rx-ant CAL
>                                 --wave-type SINE --ref internal
>                                 --wave-freq 1000
>
>                                 (It makes no difference if I use the
>                                 RX2 antenna and a loopback cable.)
>
>                                 With a sampling rate of 2.5 MHz and a
>                                 sine wave of 1 KHz, I expect to see a
>                                 sinusoidal cycle every 2500 samples.
>                                 I'm plotting them with GNU Octave and
>                                 the following commands:
>
>                                 fid =
>                                 fopen("~/uhd/host/build/examples/usrp_samples.dat",
>                                 "rb");
>                                 [sig, count] = fread(fid, Inf, "int16");
>                                 sig_c = sig(1:2:end) + j * sig(2:2:end);
>                                 plot(abs(sig_c));
>
>                                 The signal seems very noisy, and it's
>                                 pretty much gone towards the end of
>                                 the capture. Am I doing something wrong?
>
>                                 -- 
>                                 Jim Hunziker
>                                 BCI Systems and Software Engineering
>                                 jhunziker at bcisensors.com
>                                 <mailto:jhunziker at bcisensors.com>
>
>
>
>
>                         _______________________________________________
>                         USRP-users mailing list
>                         USRP-users at lists.ettus.com
>                         <mailto:USRP-users at lists.ettus.com>
>                         http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>
>
>
>
>
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com


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

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/attachments/20141029/13e02d1e/attachment-0002.html>


More information about the USRP-users mailing list