Thanks Fabian. As long as the input PPS is driven by the same RefClk that is provided to the X310, this system should be ok. You might also consider driving the PPS on the falling edge of the RefClk to ensure timing is met at the X310. There are some timing constraints here that might affect performance, but I wouldn't expect to see a 10 ns shift.
-Daniel On Thu, Sep 26, 2019 at 3:18 PM Fabian Schwartau via USRP-users < usrp-users@lists.ettus.com> wrote: > It is a self build device using a 74LS125D as buffer. The level is 3.3V > digital. > As there were no specifications around for the required input levels at > the time we needed the device, we just measured the levels coming from > the 1PPS output and replicated them. > > Am 26.09.2019 um 13:51 schrieb Daniel Jepson via USRP-users: > > Hi Fabian, Cherif, > > > > What is the external PPS device you are using? > > > > -Daniel > > > > On Thu, Sep 26, 2019 at 9:18 AM Fabian Schwartau via USRP-users > > <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>> wrote: > > > > Hi, > > I have very similar problem with X310. I am running a C++ > application, > > so I have a bit more flexibility I guess. After I do the > > set_time_unknown_pps to sync to the 1PPS signal, I run the function > > get_time_last_pps and it sometimes has an offset of 10ns (it was 5ns > > for > > an old firmware due to a bug, which was fixed a few weeks ago). If > that > > is the case I just do the sync again until the offset is zero. > > I don't know if it is an firmawre problem or if it is because the > > signal > > integrety of the 1PPS signal is not good enough. > > Maybe that is also a solution for you. > > Best regards, > > Fabian > > > > Am 25.09.2019 um 11:16 schrieb Cherif Diouf via USRP-users: > > > Hello, > > > I am working with the X310 USRP. I have two identical custom > blocks > > > feeding the RF frontends. > > > > > > flowchart > > > ----------------- > > > HW Block1 -> RF0-TX1 |---< > > > HW Block2 -> RF1-TX1 |---< > > > > > > The system is synchronized to an external PPS reference. The > > sampling > > > rate is 200 MSps and the signal bandwidth is 160 MHz for both > > channels. > > > The two HW blocks start transmitting at the exactly same time. > Time > > > resolution is 5ns. > > > In most cases the two outgoing RF signals present a 1ns time > offset. > > > Which can be understood as a phase offset. > > > > > > But From time to time there is a 6ns delay between the channels. I > > > assume this 6ns comprises the 1ns delay due to phase offset + 5 > > ns delay > > > due to misalignment of outgoing samples. > > > > > > What could be the origin of this one sample misalignement? Is it > > a way > > > to fix it? Or working close to the limits of the device should > such > > > behavior be expected? > > > > > > Thanks in advance > > > > > > Best Regards > > > Cherif > > > > > > > > > _______________________________________________ > > > USRP-users mailing list > > > USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com> > > > > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > > > > > > -- > > -------------------------------------------------- > > M.-Sc. Fabian Schwartau > > Technische Universität Braunschweig > > Institut für Hochfrequenztechnik > > Schleinitzstr. 22 > > 38106 Braunschweig > > Germany > > > > Tel.: +49-(0)531-391-2017 > > Fax: +49-(0)531-391-2045 > > Email: fabian.schwar...@ihf.tu-bs.de > > <mailto:fabian.schwar...@ihf.tu-bs.de> > > WWW: http://www.tu-braunschweig.de/ihf > > -------------------------------------------------- > > > > _______________________________________________ > > USRP-users mailing list > > USRP-users@lists.ettus.com <mailto: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 <mailto:daniel.jep...@ni.com> > > > > > > _______________________________________________ > > USRP-users mailing list > > USRP-users@lists.ettus.com > > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > > > -- > -------------------------------------------------- > M.-Sc. Fabian Schwartau > Technische Universität Braunschweig > Institut für Hochfrequenztechnik > Schleinitzstr. 22 > 38106 Braunschweig > Germany > > Tel.: +49-(0)531-391-2017 > Fax: +49-(0)531-391-2045 > Email: fabian.schwar...@ihf.tu-bs.de > WWW: http://www.tu-braunschweig.de/ihf > -------------------------------------------------- > > _______________________________________________ > 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
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