Hello Jawad,
The UHD 3.9 release changed the default GPSDO behavior. UHD does not
automatically synchronize device time to GPS time on initialization because
it's not reliable during device start-up. I'm not 100% sure about GNU
Radio's handling of these changes so will have to check before commenting
on the behavior there.
Here is a method of reliably setting the time in your own code:
1) Poll on usrp->get_mboard_sensor("gps_locked") until it returns true
2) Poll on usrp->get_time_last_pps() until a change is seen.
3) Sleep 200ms (allow NMEA string to propagate)
4) Use
"usrp->set_time_next_pps(uhd::time_spec_t(usrp->get_mboard_sensor("gps_time").to_int()+1));"
to set the time
5) Poll on usrp->get_time_last_pps() until a change is seen.
6) Sleep 200ms (allow NMEA string to propagate)
7) Verify that usrp->get_time_last_pps() and
usrp->get_mboard_sensor("gps_time") return the same time.
Regards,
Derek
On Fri, Jan 8, 2016 at 4:50 AM, Jawad Seddar <jawad.sed...@gmail.com> wrote:
> Hi all,
>
> Yesterday, I decided to update from GNU Radio 3.7.7.1 + UHD 3.8.4 to GNU
> Radio 3.7.9 + UHD 3.9.1.
>
> I used pybombs and everything went well, my OOT modules compile and my
> blocks run just like they used to.
>
> My issue comes from the time that is set on the USRP. It seems like the
> time on the device is not set to use the GPSDO. After doing some digging, I
> noticed that this commit might be responsible :
> https://github.com/EttusResearch/uhd/commit/f4f3ce2550aba933b5f4d310d82a42a41ce3f6a1
> .
>
> So I tried setting the time source as GPSDO on my USRP source block (in
> GRC) but that doesn't seem to be working. I still get something (in the
> tens of thousands) that is way below what it should be (I get the time on
> the USRP by looking at the rx_time tag available at the beginning of a
> received sample stream).
>
> If I run a python CLI and setup a usrp_source then set the time manually
> to the gps_time, then the time is somewhat correct.
>
> Am I missing a step when setting up my usrp_source in GRC?
>
> Thanks,
> Jawad
>
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