In the attachment, this is rxtime.grc. We use it to display the time of tags of received signal, and this is USRP's time? In result.png, there is Offset: 0 Source: gr uhd usrp source1 Key: rx_time Value: {0 0.956504} We can not understand it, what is it? If we want to get the time is 141757.00(UTC time or GPS time), how can we do? As detailed as possible， thank you!

Hope this helps. Offset : 0 indicates the first sample output by the USRP source Key : “rx_time” is the tag key identifying it as a receive time tag Value : {0, 0,956504} is the time value from the SDR associated with the USRP source. The time is 0.956504 seconds and is derived from the SDR’s internal clock. You can either determine the host’s time and use rx_time as the initial offset (i.e., add the two together) and then count samples and calculate the sample time based on the sample rate. Or you can set the SDR’s time. That will require either modifying the USRP source block code to accept a UHD set time command via the control port, syncing to the PC’s time, or creating a block that can access the USRP source block at runtime to set the time, or modifying the generated python for the flowgraph to set time. There are various emails on the list describing some of those approaches. There is no (AFAIK) “easy” way to set the time to UTC or some other value. Good luck, steven Steven Knudsen, Ph.D., P.Eng. www. techconficio.ca www.linkedin.com/in/knudstevenknudsen Von einem gewissen Punkt an gibt es keine Rückkehr mehr. Dieser Punkt ist zu erreichen. - Franz Kafka > On Nov 16, 2016, at 07:27, zhuimengren via USRP-users <usrp-users@lists.ettus.com> wrote: > > In the attachment, this is rxtime.grc. > We use it to display the time of tags of received signal, and this is USRP's time? > In result.png, there is > Offset: 0 Source: gr uhd usrp source1 Key: rx_time Value: {0 0.956504} > We can not understand it, what is it? > If we want to get the time is 141757.00(UTC time or GPS time), how can we do?<result.png> > As detailed as possible， thank you! > > > > > > > > > > > > > > <rxtime.grc><result.png>_______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com

Hello list, I think this is an interesting topic as it underlines an issue I've been having since the commit f4f3ce2550aba933b5f4d310d82a42a41ce3f6a1 has been in place (about a year and a half now) [1]. Before that commit, when we set the clock source and time source to GPSDO in GRC, the USRP would use the GPS time as its internal time. Since that commit has been put in place, we need to do some things that I consider to be a bit hacky in order to set the USRP time to the GPS time. I consider all the solutions that have been provided to be a bit of a hack because from a GRC point of view, blocks should just be linked together and the USRP source/sink blocks parameters (namely time source and clock source) should provide the required functionality. I'm not saying the workarounds suggested time and time again on this list and the gnuradio mailing list are difficult to put in place but they come as being counter intuitive with respect to the expected behavior. So what I have been doing so far is to revert the above mentioned commit on top of new releases of UHD and it works as I expect it to. This message might be more suited to the gnuradio mailing list. [1]: https://github.com/EttusResearch/uhd/commit/f4f3ce2550aba933b5f4d310d82a42a41ce3f6a1 Regards, Jawad 2016-11-16 17:20 GMT+01:00 Steven Knudsen via USRP-users < usrp-users@lists.ettus.com>: > Hope this helps. > > Offset : 0 indicates the first sample output by the USRP source > Key : “rx_time” is the tag key identifying it as a receive time tag > Value : {0, 0,956504} is the time value from the SDR associated with the > USRP source. The time is 0.956504 seconds and is derived from the SDR’s > internal clock. > > You can either determine the host’s time and use rx_time as the initial > offset (i.e., add the two together) and then count samples and calculate > the sample time based on the sample rate. > > Or you can set the SDR’s time. That will require either modifying the USRP > source block code to accept a UHD set time command via the control port, > syncing to the PC’s time, or creating a block that can access the USRP > source block at runtime to set the time, or modifying the generated python > for the flowgraph to set time. There are various emails on the list > describing some of those approaches. > > There is no (AFAIK) “easy” way to set the time to UTC or some other value. > > Good luck, > > steven > > > Steven Knudsen, Ph.D., P.Eng. > www. techconficio.ca > www.linkedin.com/in/knudstevenknudsen > > *Von einem gewissen Punkt an gibt es keine Rückkehr mehr. Dieser Punkt ist > zu erreichen. - Franz Kafka* > > On Nov 16, 2016, at 07:27, zhuimengren via USRP-users < > usrp-users@lists.ettus.com> wrote: > > In the attachment, this is rxtime.grc. > We use it to display the time of tags of received signal, and this is > USRP's time? > In result.png, there is > Offset: 0 Source: gr uhd usrp source1 Key: rx_time Value: {0 > 0.956504} > We can not understand it, what is it? > If we want to get the time is 141757.00(UTC time or GPS time), how can we > do?<result.png> > As detailed as possible， thank you! > > > > > > > > > > > > > > <rxtime.grc><result.png>_______________________________________________ > 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 > >

I totally agree with the “hackiness” aspect. The solutions I suggest and have implemented both suffer from “bad programming”. That is, there are dependencies introduced that are possibly impacted by future changes to GNU radio, or you end up hacking generated python (which defeats the purpose of GR, IMHO), or you are “cheating” by knowing a USRP block reference that you use in your own OOT. The latter is also a problem if, I think, you have more than one USRP attached. If I could suggest a change to the USRP block, I’d add a second sync to PC option that is “PC + 1 PPS”. Then I’d take my current approach, which is to loop on PC time until the fractional part is < 100 ms, then use set unknown PPS with the appropriate whole seconds value (2 seconds in the future). Just a suggestion… comments? Slap-down??? thanks, steven Steven Knudsen, Ph.D., P.Eng. www. techconficio.ca www.linkedin.com/in/knudstevenknudsen Der entscheidende Augenblick der menschlichen Entwicklung ist immerwährend. Darum sind die revolutionären geistigen Bewegungen, welche alles Frühere für nichtig erklären, im Recht, denn es ist noch nichts geschehen. - Franz Kafka > On Nov 17, 2016, at 01:19, Jawad Seddar via USRP-users <usrp-users@lists.ettus.com> wrote: > > Hello list, > > I think this is an interesting topic as it underlines an issue I've been having since the commit f4f3ce2550aba933b5f4d310d82a42a41ce3f6a1 has been in place (about a year and a half now) [1]. > > Before that commit, when we set the clock source and time source to GPSDO in GRC, the USRP would use the GPS time as its internal time. Since that commit has been put in place, we need to do some things that I consider to be a bit hacky in order to set the USRP time to the GPS time. > > I consider all the solutions that have been provided to be a bit of a hack because from a GRC point of view, blocks should just be linked together and the USRP source/sink blocks parameters (namely time source and clock source) should provide the required functionality. I'm not saying the workarounds suggested time and time again on this list and the gnuradio mailing list are difficult to put in place but they come as being counter intuitive with respect to the expected behavior. > > So what I have been doing so far is to revert the above mentioned commit on top of new releases of UHD and it works as I expect it to. > > This message might be more suited to the gnuradio mailing list. > > [1]: https://github.com/EttusResearch/uhd/commit/f4f3ce2550aba933b5f4d310d82a42a41ce3f6a1 <https://github.com/EttusResearch/uhd/commit/f4f3ce2550aba933b5f4d310d82a42a41ce3f6a1> > > Regards, > Jawad > > > > 2016-11-16 17:20 GMT+01:00 Steven Knudsen via USRP-users <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>>: > Hope this helps. > > Offset : 0 indicates the first sample output by the USRP source > Key : “rx_time” is the tag key identifying it as a receive time tag > Value : {0, 0,956504} is the time value from the SDR associated with the USRP source. The time is 0.956504 seconds and is derived from the SDR’s internal clock. > > You can either determine the host’s time and use rx_time as the initial offset (i.e., add the two together) and then count samples and calculate the sample time based on the sample rate. > > Or you can set the SDR’s time. That will require either modifying the USRP source block code to accept a UHD set time command via the control port, syncing to the PC’s time, or creating a block that can access the USRP source block at runtime to set the time, or modifying the generated python for the flowgraph to set time. There are various emails on the list describing some of those approaches. > > There is no (AFAIK) “easy” way to set the time to UTC or some other value. > > Good luck, > > steven > > > Steven Knudsen, Ph.D., P.Eng. > www. techconficio.ca <http://techconficio.ca/> > www.linkedin.com/in/knudstevenknudsen <http://www.linkedin.com/in/knudstevenknudsen> > > Von einem gewissen Punkt an gibt es keine Rückkehr mehr. Dieser Punkt ist zu erreichen. - Franz Kafka > >> On Nov 16, 2016, at 07:27, zhuimengren via USRP-users <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>> wrote: >> >> In the attachment, this is rxtime.grc. >> We use it to display the time of tags of received signal, and this is USRP's time? >> In result.png, there is >> Offset: 0 Source: gr uhd usrp source1 Key: rx_time Value: {0 0.956504} >> We can not understand it, what is it? >> If we want to get the time is 141757.00(UTC time or GPS time), how can we do?<result.png> >> As detailed as possible， thank you! >> >> >> >> >> >> >> >> >> >> >> >> >> >> <rxtime.grc><result.png>_______________________________________________ >> 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 <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com> > > > _______________________________________________ > 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 <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