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

Michael West michael.west at ettus.com
Thu Oct 30 15:48:12 EDT 2014


Glad to hear you figured it out.

Michael

On Thu, Oct 30, 2014 at 8:22 AM, Jim Hunziker <jhunziker at bcisensors.com>
wrote:

> 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
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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