[USRP-users] Still problems with USRP time from GPSDO

Sivan Toledo stoledo at tau.ac.il
Tue Apr 30 09:21:35 EDT 2013


Hi Josh,

Yes, here is the output from the two units. For the record, I reported this
as possible bug, but I found a way around this in my software so it does
not bother me too much. But if it's a bug it would be good to fix this.

Here are the two outputs:

pc-sivan-09:~/Projects/atlas/uhd>
../../uhd/host/build/utils/query_gpsdo_sensors ; date +%s
linux; GNU C++ version 4.6.3; Boost_104601; UHD_003.005.001-0-unknown


Creating the USRP device with: ...
-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes
-- Detecting internal GPSDO.... Found a Jackson Labs GPS
-- found
-- Setting references to the internal GPSDO
-- Initializing time to the internal GPSDO
Using Device: Single USRP:
  Device: USRP2 / N-Series Device
  Mboard 0: N200r4
  RX Channel: 0
    RX DSP: 0
    RX Dboard: A
    RX Subdev: WBXv3 RX+GDB
  TX Channel: 0
    TX DSP: 0
    TX Dboard: A
    TX Subdev: WBXv3 TX+GDB

**************************************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.
You can no longer select the external SMAs for 10 MHz or 1 PPS signaling.
****************************************************************************************************************
GPS Locked
USRP Locked to GPSDO 10 MHz Reference.

GPS and UHD Device time are NOT aligned. Try re-running the program. Double
check 1 PPS connection from GPSDO.

Printing available NMEA strings:
 PS_GPGGA:
$GPGGA,131823.00,3206.7878,N,3448.4199,E,2,09,1.0,59.3,M,17.6,M,,*6B
 PS_GPRMC: $GPRMC,131824.00,A,3206.7878,N,3448.4199,E,0.3,0.0,300413,,*01
GPS epoch time: 1367327902 seconds
UHD Device time: 1367327902 seconds

Done!

1367327904


---------------------------------------------------

pc-sivan-09:~/Projects/atlas/uhd>
../../uhd/host/build/utils/query_gpsdo_sensors ; date +%s
linux; GNU C++ version 4.6.3; Boost_104601; UHD_003.005.001-0-unknown


Creating the USRP device with: ...
-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes
-- Detecting internal GPSDO.... Found a Jackson Labs GPS
-- found
-- Setting references to the internal GPSDO
-- Initializing time to the internal GPSDO

UHD Warning:
    get_time: ValueError: get_nmea(): no $GPRMC message found
Using Device: Single USRP:
  Device: USRP2 / N-Series Device
  Mboard 0: N200r4
  RX Channel: 0
    RX DSP: 0
    RX Dboard: A
    RX Subdev: SBXv3 RX
  TX Channel: 0
    TX DSP: 0
    TX Dboard: A
    TX Subdev: SBXv3 TX

**************************************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.
You can no longer select the external SMAs for 10 MHz or 1 PPS signaling.
****************************************************************************************************************
GPS Locked
USRP Locked to GPSDO 10 MHz Reference.

UHD Warning:
    get_time: ValueError: get_nmea(): no $GPRMC message found

GPS and UHD Device time are NOT aligned. Try re-running the program. Double
check 1 PPS connection from GPSDO.

Printing available NMEA strings:
 PS_GPGGA:
$GPGGA,131822.00,3206.7913,N,3448.4214,E,1,07,1.6,49.0,M,17.6,M,,*69
 PS_GPRMC: $GPRMC,131823.00,A,3206.7910,N,3448.4214,E,0.2,0.0,300413,,*0E
GPS epoch time: 1367327901 seconds
UHD Device time: 1367327901 seconds

Done!

1367327903



On Mon, Apr 29, 2013 at 9:37 PM, Josh Blum <josh at ettus.com> wrote:

>
>
> On 04/29/2013 07:10 AM, Sivan Toledo wrote:
> > I think that my previous message was wrong, but I still have problems
> with
> > the GPSDO times from the USRP. Here is a printout from a UHD program that
> > queries the time in 4 different ways:
> >
> > usrp->get_time_now(): 1367237083:0.517574
> > usrp->get_time_last_pps():  1367237082:1.000000
> > metadata time stamp of recent RX samples:   1367237083:0.510384
> > utime() on Linux:   1367237084:0.517167
> >
> > As you can see there is a difference of a whole second between the time
> on
> > the PC, which is derived from NTP using ntpd and should be accurate to at
> > least 10ms or so, and the times on the USRP.
> >
> > The USRP is an N200 with a GPSDO fitted.
> >
> > We've experienced errors by whole seconds in two different units. Is
> this a
> > bug in the firmware or image?
> >
>
> Hey,
>
> Sorry for the trouble.
>
> Can I ask what version of UHD you are running? A few weeks ago I fixed a
> bug on the master branch related to GPSDO time, it sounds roughly like
> you describe. If you are running a stale version of master, that could
> potentially be the cause. However, if this is code from maint or a
> release then Im not sure.
>
> Can you send the output of
> <install prefix>/share/uhd/utils/query_gpsdo_sensors
>
> I think that will be revealing.
>
> -josh
>
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
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