[LinuxPPS] garmin 18 lvc versus garmin 18x lvc with pps & ntp

[Folkert van Heusden]

Hi,

Could not find any help anywhere on the web so you guys are my last
hope.
I have 2 computers running a linux PPS enabled kernel and ntp.
One of the two has a garmin 18 lvc, one has a garmin 18x lvc.

The one with the 18 lvc is neatly synced:
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*GPS_NMEA(1)     .GPS.            0 l    3   16  377    0.000    0.014   0.000  <---
-muur.intranet.v .DCFa.           1 u    6   64  377    0.113  -12.192   0.047
-thegateap.intra 134.221.205.12   2 u   13   64  377    0.663   -4.427   0.099
xtuinhuis.intran .MSFS.           1 u   43   64  376    1.834  -21.121   0.897
xSHM(0)          .MSFU.           2 l   39   64  377    0.000   26.207  16.002
-ntp1.nl.uu.net  .PPS.            1 u   18   64  377   17.628   -3.813   0.445
+chime2.surfnet. .GPS.            1 u   40   64  327   21.176   -3.315   0.123
+ntp.nmi.nl      .PPS.            1 u   36   64  377   19.826   -3.448   0.352

the other with the 18x lvc not so much:
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*GENERIC(0)      .DCFa.           0 l   50   64  377    0.000    7.370   6.659
xGPS_NMEA(0)     .GPS.            0 l    7   16  377    0.000  -657.92  11.250 <---
-ntp0.nl.uu.net  .PPS.            1 u  441 1024  377   20.147    8.310   1.973
-chime1.surfnet. .GPS.            1 u  498 1024  377   17.674    8.282   0.340
+ntp.nmi.nl      .PPS.            1 u  571 1024  377   20.065    8.279   0.383
-belle.intranet. .GPS.            1 u   37   64  376    0.097   12.165   0.062
-thegateap.intra 192.87.106.3     2 u  962 1024  176    0.095    6.811   0.720
xtuinhuis.intran .MSFS.           1 u  936 1024   76    1.971   -8.080   0.559

As you can see it's offset is huge. Somewhere between -600 and -700 and
on average around -657ms.

Once (or twice) it ran fine; offset and jitter both around 0.00xms.
Others seem to have this problem with that lvc version as well.

I verified that the system receives pps-signal:
mauer:/usr/local# for i in 1 2 3 4 5 ; do cat /sys/class/pps/pps1/assert ; sleep 1 ; done
1242845619.987661535#199682
1242845620.987661473#199683
1242845621.987660915#199684
1242845622.987660504#199685
1242845623.987660454#199686

The assert/clear is also not too short:
mauer:/sys/class/pps/pps1# cat  assert clear
1242846035.987585645#200094
1242846036.187587528#199624
so no problem there for the system to capture them.

Is there a way that i can verify that ntpd also sees these events?


Folkert van Heusden

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