Fabian, I noticed on the SN74LS125A datasheet the minimum input voltage is 4.75V. Is this the correct part that you're using?
-Daniel On Fri, Sep 27, 2019 at 9:27 AM Daniel Jepson <daniel.jep...@ettus.com> wrote: > 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 > -- Daniel Jepson Digital Hardware Engineer National Instruments O: +1.512.683.6163 daniel.jep...@ni.com
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