[USRP-users] GPS and UHD Time Alignment

devin kelly dwwkelly at gmail.com
Thu Mar 24 11:59:04 EDT 2016


The issue is that as soon as I align the two clocks they become
un-aligned.  So if I run the master branch version of query_gpsdo_sensors
back-to-back (without interruption) the UHD and GPS clocks aren't aligned
_both_ times.

I do this with the 3.9.2 version of the UHD and FPGA firmware/image, so
part of my question is for UHD 3.9.{0,1,2} is this a problem with just
query_gpsdo_sensors or is there something wrong with library or FPGA image
too?

On Wed, Mar 23, 2016 at 5:14 PM, Michael West via USRP-users <
usrp-users at lists.ettus.com> wrote:

> Hi Devin,
>
> The version of the query_gpsdo_sensor utility in UHD 3.9.2 and 3.9.3 does
> not work properly on the X310.  You did the correct thing by downloading
> the version at the head of the master branch.  That version explicitly sets
> the time and clock sources to "gpsdo", where the other versions of the
> utility assumed the sources were set to "gpsdo" by default.  UHD 3.10.0
> will have the corrected version of the utility.
>
> Regards,
> Michael
>
> On Wed, Mar 23, 2016 at 1:57 PM, Marcus D. Leech via USRP-users <
> usrp-users at lists.ettus.com> wrote:
>
>> On 03/23/2016 04:29 PM, devin kelly via USRP-users wrote:
>>
>> Hello,
>>
>> I'm on UHD 3.9.2 and I've been having some problems with aligning the UHD
>> time and GPS time on my X310.  My GPS, as far as I can tell, acquires and
>> maintains lock fine.  However, everytime I run query_gpsdo_sensors the UHD
>> and GPS time are not aligned (UHD time is always some low number like 1,2
>> or 3).
>>
>> I downloaded the the master copy query_gpsdo_sensors here:
>>
>>
>> https://github.com/EttusResearch/uhd/blob/master/host/utils/query_gpsdo_sensors.cpp
>>
>> And built it against 3.9.2, everything works seems to work fine when I
>> run it:
>>
>> Time source is now gpsdo
>> GPS Locked
>> Setting the reference clock source to "gpsdo"...
>>
>> Clock source is now gpsdo
>> **************************************Helpful Notes on Clock/PPS
>> Selection**************************************
>> As you can see, the default 10 MHz Reference and 1 PPS signals are now
>> from the GPSDO.
>> If you would like to use the internal reference(TCXO) in other
>> applications, you must configure that explicitly.
>>
>> ****************************************************************************************************************
>> USRP Locked to GPSDO 10 MHz Reference.
>>
>> GPS and UHD Device time are NOT aligned;
>> last_pps: 3 vs gps: 1458764120. Trying to set the device time to GPS
>> time...
>> --     1) catch time transition at pps edge
>> --     2) set times next pps (synchronously)
>> last_pps: 1458764124 vs gps: 1458764124.
>> GPS and UHD Device time are aligned.
>> Printing available NMEA strings:
>> GPS_GPGGA:
>> $GPGGA,201524.00,4227.5889,N,07116.0425,W,2,10,1.2,86.8,M,-33.1,M,,*68
>> GPS_GPRMC:
>> $GPRMC,201524.00,A,4227.5889,N,07116.0425,W,0.0,0.0,230316,,*29
>> GPS Epoch time at last PPS: 1458764124.00000 seconds
>> UHD Device time last PPS:   1458764124.00000 seconds
>> UHD Device time right now:  1458764124.24561 seconds
>> PC Clock time:              1458764124 seconds
>>
>> GPS and UHD time aren't aligned but query_gpsdo_senors aligns them for me
>> fine.  However if I run querry_gpsdo_sensors again the clocks are
>> un-aligned again!
>>
>> Time source is now gpsdo
>> GPS Locked
>> Setting the reference clock source to "gpsdo"...
>>
>> Clock source is now gpsdo
>> **************************************Helpful Notes on Clock/PPS
>> Selection**************************************
>> As you can see, the default 10 MHz Reference and 1 PPS signals are now
>> from the GPSDO.
>> If you would like to use the internal reference(TCXO) in other
>> applications, you must configure that explicitly.
>>
>> ****************************************************************************************************************
>> USRP Locked to GPSDO 10 MHz Reference.
>>
>> GPS and UHD Device time are NOT aligned;
>> last_pps: 3 vs gps: 1458764770. Trying to set the device time to GPS
>> time...
>> --     1) catch time transition at pps edge
>> --     2) set times next pps (synchronously)
>> last_pps: 1458764774 vs gps: 1458764774.
>> GPS and UHD Device time are aligned.
>> Printing available NMEA strings:
>> GPS_GPGGA:
>> $GPGGA,202614.00,4227.5830,N,07116.0439,W,2,11,1.0,80.9,M,-33.1,M,,*60
>> GPS_GPRMC:
>> $GPRMC,202614.00,A,4227.5830,N,07116.0439,W,0.2,0.0,230316,,*27
>> GPS Epoch time at last PPS: 1458764774.00000 seconds
>> UHD Device time last PPS:   1458764774.00000 seconds
>> UHD Device time right now:  1458764774.24745 seconds
>> PC Clock time:              1458764774 seconds
>>
>> Done!
>>
>> What's going on here?  I think the newest UHD release is 3.9.3 so I could
>> try that but could there be some other issue?
>>
>> Thanks for any help,
>>
>> Devin
>>
>>
>> _______________________________________________
>> USRP-users mailing listUSRP-users at lists.ettus.comhttp://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>
>> When you re-run, do you do so immediately?   What's the scenario?  What
>> do you do between running query_gpsdo_sensor instances?
>>
>>
>>
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>> USRP-users at lists.ettus.com
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>>
>>
>
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