GPS / time sync problems on jet

Sometimes if jet reboots, the time gets lost. It is evident from MCSPU log messages on jet:

May 17 05:31:19.180: LFBG RTracker: ERROR: DSP mjd differs from Linux mjd by -3.153600e+07 sec.
May 17 05:31:19.210: RDG RTracker: ERROR: DSP mjd differs from Linux mjd by -3.153600e+07 sec.
May 17 05:31:19.210: RFBG RTracker: ERROR: DSP mjd differs from Linux mjd by -3.153600e+07 sec.
May 17 05:31:19.215: LDG RTracker: ERROR: DSP mjd differs from Linux mjd by -3.153600e+07 sec.
...

Rotators going in to fault, and PCS showing bizarre results.

In the event log:

Tue May 17 05:31:19.180 2016 57525.23008310170 1 MCS  MCS.MCSPU.Tracker.timeDisagreement null  DSP has MJDsec=4.938643915151308e+09. Linux has MJDsec= 4.970179915179786e+09. Difference =-3.153600002847767e+07
Tue May 17 05:31:19.210 2016 57525.23008345407 1 MCS  MCS.MCSPU.Tracker.timeDisagreement null  DSP has MJDsec=4.938643915161445e+09. Linux has MJDsec= 4.970179915210274e+09. Difference =-3.153600004882908e+07
Tue May 17 05:31:19.210 2016 57525.23008345627 1 MCS  MCS.MCSPU.Tracker.timeDisagreement null  DSP has MJDsec=4.938643915151308e+09. Linux has MJDsec= 4.970179915210471e+09. Difference =-3.153600005916309e+07
Tue May 17 05:31:19.215 2016 57525.23008351125 1 MCS  MCS.MCSPU.Tracker.timeDisagreement null  DSP has MJDsec=4.938643915161445e+09. Linux has MJDsec= 4.970179915215230e+09. Difference =-3.153600005378532e+07
...

From Dan on 20160516:
The GPS receiver was fine. The BC635 PCI chip lost the year. (I say \x93GPS\x94 rather than BC635 since it\x92s more understandable.) The actual GPS receiver is fine and nothing was changed.

The DSPs get time from the GPS receiver via the BC635 as IRIG, which doesn\x92t include the year. That\x92s set via a user app (/home/dsp/bin/bc635pci). If jet crashes in the the right way, we seem to lose a year in

the BC635 chip. I ran the application, reset the year, and we restarted the MCSPU.

This topic: Software > WebHome > MountainTroubleshooting > JetGPSProblem
Topic revision: 19 Oct 2017, TomSargent
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