[ntp:questions] Motorola Oncore Surveyed Position

Miguel Gonçalves mail at miguelgoncalves.com
Tue Sep 6 15:32:13 UTC 2011


Hi!

Thanks for the help!

My /etc/ntp.oncore.0 file is this (I disabled SHMEM)

MODE 1
LAT 41.1745319
LON -8.6560764
HT 146.72 M
HARDPPS
#SHMEM /etc/oncore.0
TRAIM YES
DELAY 25 NS
CLEAR
MASK 0

I'm getting one strange thing:

oncore# ntpq -p
     remote           refid      st t when poll reach   delay   offset
jitter
==============================================================================
xGPS_ONCORE(0)   .GPS.            0 l    4   16  377    0.000  -15045.
2.016
 canon.inria.fr  .GPSi.           1 u   69   64  377   49.013  -15043.
9.609
 ptbtime1.ptb.de .PTB.            1 u   52   64  377   66.784  -15043.
8.614
 ntp.inrim.it    .CTD.            1 u   56   64  377   52.119  -15043.
8.875

The GPS is off by 15 secs. Is this the GPS-UTC delta? Why is this happening?

Can anyone help?

Thanks!

Cheers,
Miguel


On 6 September 2011 15:31, Thomas Laus <lausts at acm.org> wrote:

> On 2011-09-06, Miguel Gon?alves <mail at miguelgoncalves.com> wrote:
> > I switched again to mode 4 and started again to see if I missed
> something. I
> > believe I'll only have to wait 10000 seconds = 2 hours and 46 minutes...
> not
> > much. :-)
> >
> > Unfortunatelly clockstats doesn't show position, only time. I believe
> this
> > is because it's in position lock (0D?) mode. Here's a sample:
> >
> > By the way... I was looking at the clockstats file and noticed that when
> I
> > switched to mode 4 as I said earlier I got this
> >
> > 55810 40560.366 127.127.30.0 ONCORE[0]: Loading Posn from SHMEM
> > 55810 40560.367 127.127.30.0 ONCORE[0]: Setting Posn and Time after
> Loading
> > Almanac
> > 55810 40562.091 127.127.30.0 ONCORE[0]: Posn:
> > 55810 40562.091 127.127.30.0 ONCORE[0]: Lat = N  41.1745319deg,    Long =
> > W   8.6560764deg,    Alt = 146.72m (481.36ft) GPS
> > 55810 40562.091 127.127.30.0 ONCORE[0]: Lat = N  41deg 10.4719m,   Long =
> > W   8deg 39.36458m,  Alt =  146.72m ( 481.36ft) GPS
> > 55810 40562.091 127.127.30.0 ONCORE[0]: Lat = N  41deg 10m 28.32s, Long =
> > W   8deg 39m 21.88s, Alt =  146.72m ( 481.36ft) GPS
> > 55810 40564.365 127.127.30.0 ONCORE[0]: Waiting for Almanac
> > 55810 40567.365 127.127.30.0 ONCORE[0]: Have now loaded an ALMANAC
> > 55810 40567.365 127.127.30.0 ONCORE[0]: state = ONCORE_RUN
> >
> > It seems this is my location... :-) Now you know where I live! :-)
> >
> > So the position is stored in the shared memory and when I reset the unit
> > (mode 4) it uses the position stored in there.
> >
> > Anyone help care to comment this?
> >
> This is from the refclock_oncore.c file.
>
> /*
>  * If we don't find any then we don't have the cable delay or PPS
>  * offset and we choose MODE (4) below.
>  *
>  * Five Choices for MODE
>  *    (0) ONCORE is preinitialized, don't do anything to change it.
>  *        nb, DON'T set 0D mode, DON'T set Delay, position...
>  *    (1) NO RESET, Read Position, delays from data file, lock it in,
>  *        go to 0D mode.
>  *    (2) NO RESET, Read Delays from data file, do SITE SURVEY to get
>  *        position, lock this in, go to 0D mode.
>  *    (3) HARD RESET, Read Position, delays from data file, lock it
>  *        in, go to 0D mode.
>  *    (4) HARD RESET, Read Delays from data file, do SITE SURVEY to
>  *        get position, lock this in, go to 0D mode.
>  *     NB. If a POSITION is specified in the config file with
>  *     mode=(2,4) [SITE SURVEY] then this position is set as the INITIAL
> position of the
>  *     ONCORE.  This can reduce the time to first fix.
>  *
>
>  -------------------------------------------------------------------------------
>  * Note that an Oncore UT without a battery backup retains NO
>  information if it is power cycled, with a Battery Backup it remembers the
> almanac,
>  etc. For an Oncore VP, there is an eeprom that will contain this data,
>  along with the option of Battery Backup.
>
>  * So a UT without Battery Backup is equivalent to doing a HARD RESET
>  on each power cycle, since there is nowhere to store the data.
>  If we open one or the other of the files, we read it looking for
>  MODE, LAT, LON, (HT, HTGPS, HTMSL), DELAY, OFFSET, ASSERT, CLEAR,
>  HARDPPS, STATUS, POSN3D, POSN2D, CHAN, TRAIM then initialize using
>  method MODE.  For Mode = (1,3) all of (LAT, LON, HT) must be present
>  or mode reverts to (2,4).
> */
> Your ntp.oncore.0 file will need to list your location:
>
> This is from my file
>
> HARDPPS
> PPS_CAPTUREASSERT
> MODE 1
> LON -84.2017844758
> LAT 40.7762210511
> HT 223.445
> DELAY 92.1 ns
>
> This skips the receiver reset and loads my coordinates.  Once the
> receiver has a valid almanac, it will serve time.  I am also using
> FreeBSD, but don't use SHMEM.  You should be able to just link your
> serial port to the correct device using devfs.conf
>
> oncore.pps.0 ->cuau0
> oncore.serial.0 ->cuau0
>
> Tom
>
> --
> Public Keys:
> PGP KeyID = 0x5F22FDC1
> GnuPG KeyID = 0x620836CF
>
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