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

Jim Hunziker jhunziker at bcisensors.com
Thu Oct 30 11:22:07 EDT 2014


Sorry - you can stop looking at this problem. With the loopback cable, our
I and Q plots look like yours, and our magnitude plot is pretty much
constant (after the initial settling time).


-- 
Jim Hunziker
BCI Systems and Software Engineering
(973) 348-9299
jhunziker at bcisensors.com

On Thu, Oct 30, 2014 at 10:06 AM, Jim Hunziker <jhunziker at bcisensors.com>
wrote:

> Linked below is my usrp_samples.dat generated with the following command:
>
> ./txrx_loopback_to_file --tx-args addr=192.168.10.2 --rx-args
> addr=192.168.10.2 --nsamps=25000000 --tx-rate 25000000 --rx-rate 25000000
> --tx-freq 5600000000 --rx-freq 5600000000 --rx-ant CAL --wave-type SINE
> --ref internal --wave-freq 1000000 --tx-gain 15 --rx-gain 15 --type float
>
> If the file looks OK to you in your GRC flowgraph, could you send that
> flowgraph to me? (I don't know how to use GRC, but I'll figure it out.)
>
> If it doesn't look OK, please send instructions on how to exactly
> replicate your hardware setup.
>
> Thanks.
> ​​
> ​Link to file (you might need to be logged into a Google account):
> usrp_samples.zip
> <https://drive.google.com/file/d/0B8PLzsIbPgE9cFNHU1pjamJSa1E/view?usp=sharing>
>
> --
> Jim Hunziker
> BCI Systems and Software Engineering
> jhunziker at bcisensors.com
>
> On Wed, Oct 29, 2014 at 6:32 PM, Michael West <michael.west at ettus.com>
> 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
>>
>> On Wed, Oct 29, 2014 at 12:29 PM, Jim Hunziker <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
>>>
>>> On Mon, Oct 27, 2014 at 4:05 PM, Jim Hunziker <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
>>>>
>>>> On Mon, Oct 27, 2014 at 1:32 PM, Michael West <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> 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
>>>>>>
>>>>>> On Fri, Oct 24, 2014 at 5:55 PM, Michael West <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> 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
>>>>>>>>
>>>>>>>> On Wed, Oct 22, 2014 at 4:42 PM, Jim Hunziker <
>>>>>>>> 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
>>>>>>>>>
>>>>>>>>> On Wed, Oct 22, 2014 at 12:15 PM, Jim Hunziker <
>>>>>>>>> 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
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> USRP-users mailing list
>>>>>>>> USRP-users at lists.ettus.com
>>>>>>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/attachments/20141030/6cd3c087/attachment-0002.html>


More information about the USRP-users mailing list