Hi usrp users, Is there any documentation which described what is returned by the "gps_servo" sensor ? It returns several things, but what are they signification ? Thanks. Matis

Hi Matis, reading the gps_servo sensor leads to sending the "SERV:TRAC 1" message to the GPSDO. That in turn replies with a device-specific string. In your case, that should have the following fields: date PPS count fine DAC UTC offset [10^-9s] Freq. Error Estimate Nr. of visible Satellites Nr. of tracked Satellites Locked State Health State With a space between every item. The lock state has the following possible values: 0 OCXO heat-up 1 Holdover (no lock) 2 Locking (training) 5 Holdover, but oscillator is still PLL'ed (for 100s after GPS loss) 6 Fully locked The health states are just a binary mask representing possible error states, so in perfect operation 0x0 is desirable, and, counting from the least significant bit: (I'll omit the less interesting bits – if some DAC maxes out doesn't really concern you as a user, for example, the effect of phase not being correct might in fact be very relevant to you!) *Bit** * *Meaning** * 1<<2 phase offset to UTC > 0.25 µs 1<<3 run time < 5 min 1<<4 been in holdover for > 1 min 1<<5 freq. estimate out of plausability bounds 1<<8 ADEV at 100 s > 100 ns (drift > 1ppb) 1<<9 system operational change in last 3min Best regards, Marcus On 12/16/2016 12:00 PM, Matis Alun via USRP-users wrote: > Hi usrp users, > > Is there any documentation which described what is returned by the "gps_servo" sensor ? > It returns several things, but what are they signification ? > > Thanks. > > Matis > > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com

thanks a lot! matis Le 16/12/2016 à 17:35, Marcus Müller via USRP-users a écrit : > > Hi Matis, > > reading the gps_servo sensor leads to sending the "SERV:TRAC 1" message to the GPSDO. > > That in turn replies with a device-specific string. In your case, that should have the > following fields: > > date > PPS count > fine DAC > UTC offset [10^-9s] > Freq. Error Estimate > Nr. of visible Satellites > Nr. of tracked Satellites > Locked State > Health State > > With a space between every item. > > The lock state has the following possible values: > 0 > OCXO heat-up > 1 > Holdover (no lock) > 2 > Locking (training) > 5 > Holdover, but oscillator is still PLL'ed (for 100s after GPS loss) > 6 > Fully locked > > > The health states are just a binary mask representing possible error states, so in > perfect operation 0x0 is desirable, and, counting from the least significant bit: > (I'll omit the less interesting bits – if some DAC maxes out doesn't really concern you > as a user, for example, the effect of phase not being correct might in fact be very > relevant to you!) > *Bit** > * *Meaning** > * > 1<<2 > phase offset to UTC > 0.25 µs > 1<<3 > run time < 5 min > 1<<4 > been in holdover for > 1 min > 1<<5 > freq. estimate out of plausability bounds > 1<<8 > ADEV at 100 s > 100 ns (drift > 1ppb) > 1<<9 > system operational change in last 3min > > > > Best regards, > > Marcus > > > On 12/16/2016 12:00 PM, Matis Alun via USRP-users wrote: >> Hi usrp users, >> >> Is there any documentation which described what is returned by the "gps_servo" sensor ? >> It returns several things, but what are they signification ? >> >> Thanks. >> >> Matis >> >> >> _______________________________________________ >> 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

If I record the "UTC offset" field during time, should I obtain the specification of the GPSDO which is 50 ns rms ? It seems that the value is very often less than 10 ns... Matis Le 16/12/2016 à 17:35, Marcus Müller via USRP-users a écrit : > > Hi Matis, > > reading the gps_servo sensor leads to sending the "SERV:TRAC 1" message to the GPSDO. > > That in turn replies with a device-specific string. In your case, that should have the > following fields: > > date > PPS count > fine DAC > UTC offset [10^-9s] > Freq. Error Estimate > Nr. of visible Satellites > Nr. of tracked Satellites > Locked State > Health State > > With a space between every item. > > The lock state has the following possible values: > 0 > OCXO heat-up > 1 > Holdover (no lock) > 2 > Locking (training) > 5 > Holdover, but oscillator is still PLL'ed (for 100s after GPS loss) > 6 > Fully locked > > > The health states are just a binary mask representing possible error states, so in > perfect operation 0x0 is desirable, and, counting from the least significant bit: > (I'll omit the less interesting bits – if some DAC maxes out doesn't really concern you > as a user, for example, the effect of phase not being correct might in fact be very > relevant to you!) > *Bit** > * *Meaning** > * > 1<<2 > phase offset to UTC > 0.25 µs > 1<<3 > run time < 5 min > 1<<4 > been in holdover for > 1 min > 1<<5 > freq. estimate out of plausability bounds > 1<<8 > ADEV at 100 s > 100 ns (drift > 1ppb) > 1<<9 > system operational change in last 3min > > > > Best regards, > > Marcus > > > On 12/16/2016 12:00 PM, Matis Alun via USRP-users wrote: >> Hi usrp users, >> >> Is there any documentation which described what is returned by the "gps_servo" sensor ? >> It returns several things, but what are they signification ? >> >> Thanks. >> >> Matis >> >> >> _______________________________________________ >> 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

Hi Matis, The UTC offset value is a measurement of the current offset and it will vary. It should be within the specification of +/-50ns. Values less than 10ns are not unexpected. Regards, Michael On Mon, Dec 19, 2016 at 2:42 PM, Matis Alun via USRP-users < usrp-users@lists.ettus.com> wrote: > If I record the "UTC offset" field during time, should I obtain the > specification of the GPSDO which is 50 ns rms ? > It seems that the value is very often less than 10 ns... > > Matis > > Le 16/12/2016 à 17:35, Marcus Müller via USRP-users a écrit : > > Hi Matis, > > reading the gps_servo sensor leads to sending the "SERV:TRAC 1" message to > the GPSDO. > > That in turn replies with a device-specific string. In your case, that > should have the following fields: > date > PPS count > fine DAC > UTC offset [10^-9s] > Freq. Error Estimate > Nr. of visible Satellites > Nr. of tracked Satellites > Locked State > Health State > > With a space between every item. > The lock state has the following possible values: > 0 > OCXO heat-up > 1 > Holdover (no lock) > 2 > Locking (training) > 5 > Holdover, but oscillator is still PLL'ed (for 100s after GPS loss) > 6 > Fully locked > > The health states are just a binary mask representing possible error > states, so in perfect operation 0x0 is desirable, and, counting from the > least significant bit: > (I'll omit the less interesting bits – if some DAC maxes out doesn't > really concern you as a user, for example, the effect of phase not being > correct might in fact be very relevant to you!) > *Bit* > *Meaning* > 1<<2 > phase offset to UTC > 0.25 µs > 1<<3 > run time < 5 min > 1<<4 > been in holdover for > 1 min > 1<<5 > freq. estimate out of plausability bounds > 1<<8 > ADEV at 100 s > 100 ns (drift > 1ppb) > 1<<9 > system operational change in last 3min > > > Best regards, > > Marcus > > On 12/16/2016 12:00 PM, Matis Alun via USRP-users wrote: > > Hi usrp users, > > Is there any documentation which described what is returned by the "gps_servo" sensor ? > It returns several things, but what are they signification ? > > Thanks. > > Matis > > > _______________________________________________ > USRP-users mailing listUSRP-users@lists.ettus.comhttp://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > > > > _______________________________________________ > USRP-users mailing listUSRP-users@lists.ettus.comhttp://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 > >