Hi Serge, I have tried to reproduce the issue on an N310 and X310 with no success. I tried several versions of UHD (including v3.13.1.0-rc1) on both and the time alignment was always good and the benchmark_rate with the increased INIT_DEALY always worked as expected. Can you try with the head of the UHD-3.13 branch and see if you still see the same issues? If so, please provide the modified tx_timed_samples example you are using along with the command being issued. A picture of what you are seeing on the scope would also be helpful.
Regards, Michael On Mon, Nov 12, 2018 at 9:54 PM Michael West <michael.w...@ettus.com> wrote: > Hi Serge, > > Thank you for making us aware of the issues. We are looking into them and > consider them a priority. We will let you know what we find. > > Regards, > Michael > > On Fri, Nov 9, 2018 at 11:04 AM Serge Malo via USRP-users < > usrp-users@lists.ettus.com> wrote: > >> Hi all, >> >> I have made another test today, I want to report the results here. >> >> *Issue #1* >> I have modified the tx_timed_samples example, simply such that it >> transmits on both channels of the X300. >> Using a frequency of 1.57542GHz for both channels, I was able to measure >> on a scope a time offset of 320ns between RF A and RF B. >> Technically, Ettus R&D should be able to reproduce this offset easily. >> >> *Issue #2:* >> Yesterday, I wrote that "timed commands" seemed to be broken with UHD >> 3.13.1.0 RC1. Here are more details: >> "timed samples" do work correctly with the UHD example tx_timed_samples. >> However, "timed samples" do not work with the UHD example benchmark_rate. >> You can reproduce the problem this way, on a X300, connected to an >> Octoclock: >> 1) Change the value of INIT_DELAY to 5.0s >> 2) Recompile benchmark_rate, and try this command: >> ./benchmark_rate --args addr=192.168.40.2 --tx_rate=25000000 >> --tx_cpu=sc16 --ref=external --pps=external --channels=0,1 >> >> You will see that the TX starts immediately, instead of at time 5.0s. >> >> Please, let us know if you aware of those issues, and if you need help to >> reproduce or investigate them. >> >> Best regards, >> Serge >> >> >> On Thu, 8 Nov 2018 at 23:59, Marcus D. Leech via USRP-users < >> usrp-users@lists.ettus.com> wrote: >> >>> On 11/08/2018 03:13 PM, Serge Malo via USRP-users wrote: >>> >>> Hi all, >>> >>> Thanks for the extra comments Mark. >>> >>> Just to be clear: I'm not talking about phase offset between RF Outputs, >>> but only time offset. >>> (Once time offset is fixed, we will try to have phase-coherent RF >>> outputs). >>> >>> I have made other measurements today, here are the results. >>> I'm transmitting a signal at 1.57542GHz, and a second signal at >>> 1.2276GHz. >>> Sample Rate on N310: 25.6Msps (MCR of 153.6Mhz) >>> Sample Rate on X300: 25.0Msps (MCR of 200Mhz) >>> Using External Clock and External PPS from Octoclock >>> 1) Using X300 (RF A and RF B) and UHD 3.10.3.0, we see les than 3ns time >>> offset (See image here: link >>> <https://drive.google.com/file/d/1FBC3CHOhGO4xLdJU3LhjB0pTjexNpJik/view?usp=sharing> >>> ) >>> 2) Using X300 (RF A and RF B) and UHD 3.13.1.0 RC1, we see 7300us time >>> offset (See image here: link >>> <https://drive.google.com/file/d/1mV2XrUVz1PC4boi0BzUmxFcWo2b8zj3Y/view?usp=sharing> >>> ) >>> 3) Using N310 (RF 0 and RF 2) and UHD 3.13.1.0 RC1, we also see 7300us >>> time offset. >>> >>> Important: the "timed commands" seem to be broken in UHD 3.13.1.0, >>> either for X300 or N310. >>> When we change the time_spec of the first "send" call, the time at which >>> the samples are transmitted does not change. For example, I tried to set >>> tie_spec to 10s, but the Tx starts right away. This was working correctly >>> with UHD 3.10.3.0 >>> >>> Let me know if you have ideas I could try. >>> >>> Best regards, >>> Serge >>> >>> Serge: >>> >>> The fact that this affects both X310 and N310 is a bit disturbing--the >>> device-side codebase is quite different on the two boxes. I'm engaging >>> Ettus R&D internally to see if this can be reproduced. >>> >>> >>> >>> >>> On Thu, 8 Nov 2018 at 14:44, Mark Wagner <m2wag...@eng.ucsd.edu> wrote: >>> >>>> Here's a google drive link with images of the phase drift between rx4 >>>> and tx 1&2, and tx 3&4 >>>> >>>> https://drive.google.com/open?id=1Bg6F0WHzzwVhpFBlrlfqJgpGg9JtTczH >>>> >>>> On Thu, Nov 8, 2018 at 11:32 AM Mark Wagner <m2wag...@eng.ucsd.edu> >>>> wrote: >>>> >>>>> Hi guys, >>>>> >>>>> Maybe I could jump in and share some related results. My group has >>>>> been developing a MIMO system with N310 units. We did a test sounding >>>>> recently where we sent 4, length 4096, orthogonal multitone signals from >>>>> the transmitters to the receivers and processed the data by finding the >>>>> channel response between each transmitter and receiver pair (16 in total) >>>>> and recording the magnitude and phase of the arrival spikes between each >>>>> pair. >>>>> >>>>> We took several seconds of data and processed it in length 4096 chunks >>>>> (around 1500 chunks in total) and looked at the phase difference between >>>>> transmitter pairs as time progressed. Since transmitters 1 and 2 are >>>>> sharing an LO and our setup was not moved during the sounding we expected >>>>> to see a constant phase difference between transmitters 1 and 2 and a >>>>> single receiver (same with tx 3 and 4), but we saw some drift. Worse yet, >>>>> not all LO sharing pairs drifted in the same way, some didn't drift much >>>>> at >>>>> all while some drifted in linear or non-linear patterns. >>>>> >>>>> If you're all fine with me breaking the rules I can attach some png >>>>> images of what we recorded so you can see what it looks like. Later this >>>>> week we'll repeat the experiment but leave the machines running longer to >>>>> see if the drift diminishes as the machines run longer. >>>>> >>>>> Cheers, >>>>> -Mark >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> On Thu, Nov 8, 2018 at 9:03 AM Daniel Jepson via USRP-users < >>>>> usrp-users@lists.ettus.com> wrote: >>>>> >>>>>> Hi Serge, >>>>>> >>>>>> Are you measuring the phase offset between the TX0 and TX2 signals in >>>>>> a steady-state case, or the time difference in the start of those >>>>>> signals? >>>>>> >>>>>> In the former case, your results could be impacted by the lack of >>>>>> internal LO sharing between daughterboards. I would fully expect an >>>>>> unknown >>>>>> phase offset between channels 0 and 2 every time you reconfigure the >>>>>> device. In the latter case, it sounds like a start trigger mismatch like >>>>>> Marcus mentioned. >>>>>> >>>>>> Can you share more details as to how you're measuring the phase >>>>>> offset? >>>>>> >>>>>> Thanks, >>>>>> -Daniel >>>>>> >>>>>> >>>>>> >>>>>> On Thu, Nov 8, 2018 at 5:30 AM Serge Malo via USRP-users < >>>>>> usrp-users@lists.ettus.com> wrote: >>>>>> >>>>>>> Yes: we are using UHD 3.13.1.0 RC1, with the latest file system >>>>>>> image >>>>>>> >>>>>>> I can try to use lower tx start times to see if the time offset >>>>>>> changes with that. >>>>>>> >>>>>>> Thanks, >>>>>>> Serge >>>>>>> >>>>>>> On Wed, 7 Nov 2018 at 21:44, Marcus D. Leech < >>>>>>> patchvonbr...@gmail.com> wrote: >>>>>>> >>>>>>>> On 11/07/2018 09:31 PM, Serge Malo wrote: >>>>>>>> >>>>>>>> Yes: >>>>>>>> We only use one streamer for all RF outputs, and send time_spec >>>>>>>> with each call to the streamer's send method. >>>>>>>> We reset the internal time with set_time_unkown_pps(0), and program >>>>>>>> the first samples to be streamed at a time of 0.800s. >>>>>>>> It is basically the same code we used on the X300/X310. >>>>>>>> >>>>>>>> Thanks, >>>>>>>> Serge >>>>>>>> >>>>>>>> Well, that is quite strange--the magnitude of the time offsets is >>>>>>>> larger than I would expect. >>>>>>>> >>>>>>>> Perhaps someone from the N310 team can comment? >>>>>>>> >>>>>>>> Serge, are you using the latest UHD and system image versions for >>>>>>>> the N310? >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> On Wed, 7 Nov 2018 at 21:03, Marcus D. Leech via USRP-users < >>>>>>>> usrp-users@lists.ettus.com> wrote: >>>>>>>> >>>>>>>>> On 11/07/2018 08:53 PM, Serge Malo via USRP-users wrote: >>>>>>>>> >>>>>>>>> Hi all, >>>>>>>>> >>>>>>>>> We are trying to send 4 synchronous signals from the 4 Tx ports of >>>>>>>>> the N310. >>>>>>>>> We are using UHD 3.13.1.0 RC1 under Ubuntu. >>>>>>>>> Central Freq = 1575.42 GHz and 1227.6 MHz >>>>>>>>> Master Clock rate = 153.6 MHz >>>>>>>>> >>>>>>>>> We would expect to have less than 3ns offset between all TX ports >>>>>>>>> of the N310, like we do with the X300/X310. However, we have measured >>>>>>>>> 4700ns between TX RF ports 0 and port 2. >>>>>>>>> We have tried the next things with no more success: >>>>>>>>> - Sampling rates of 25.6MSps, 38.4Msps, 76.8Msps >>>>>>>>> - Init with the device options "init_cals=ALL" and "force_reinit=1" >>>>>>>>> - Use the internal GPSDO >>>>>>>>> - Use clock_source=external and time_source=external (from an >>>>>>>>> Octoclock). >>>>>>>>> >>>>>>>>> Can you tell us: >>>>>>>>> -What time offset between TX RF ports we should expect to achieve? >>>>>>>>> -Is there anything else we can try to reduce this offset to less >>>>>>>>> than 3ns? >>>>>>>>> >>>>>>>>> Best regards, >>>>>>>>> Serge >>>>>>>>> >>>>>>>>> >>>>>>>>> How are you setting up your TX streamer? Is it time-tagged to >>>>>>>>> start at a particular device time? >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> _______________________________________________ >>>>>>>>> USRP-users mailing list >>>>>>>>> USRP-users@lists.ettus.com >>>>>>>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>>>>>>>> >>>>>>>> >>>>>>>> _______________________________________________ >>>>>>> USRP-users mailing list >>>>>>> USRP-users@lists.ettus.com >>>>>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>>>>>> >>>>>> >>>>>> >>>>>> -- >>>>>> >>>>>> Daniel Jepson >>>>>> >>>>>> Digital Hardware Engineer >>>>>> >>>>>> National Instruments >>>>>> >>>>>> >>>>>> >>>>>> O: +1.512.683.6163 >>>>>> >>>>>> daniel.jep...@ni.com >>>>>> _______________________________________________ >>>>>> USRP-users mailing list >>>>>> USRP-users@lists.ettus.com >>>>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>>>>> >>>>> >>>>> >>>>> -- >>>>> Mark Wagner >>>>> University of California San Diego >>>>> Electrical and Computer Engineering >>>>> >>>>> >>>> >>>> >>>> -- >>>> Mark Wagner >>>> University of California San Diego >>>> Electrical and Computer Engineering >>>> >>>> >>> >>> >>> _______________________________________________ >>> USRP-users mailing >>> listUSRP-users@lists.ettus.comhttp://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>> >>> >>> _______________________________________________ >>> USRP-users mailing list >>> USRP-users@lists.ettus.com >>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>> >> _______________________________________________ >> USRP-users mailing list >> USRP-users@lists.ettus.com >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >
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