40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log  Not logged in ELOG logo
Entry  Wed Jun 8 13:50:39 2016, jamie, Configuration, CDS, Spectracom IRIG-B card installed on fb1 
    Reply  Thu Jun 9 13:28:07 2016, jamie, Configuration, CDS, Spectracom IRIG-B card installed on fb1 
       Reply  Fri Jun 10 12:09:01 2016, jamie, Configuration, CDS, IRIG-B debugging 
          Reply  Fri Jun 10 12:21:54 2016, jamie, Configuration, CDS, GPS receiver not resetting properly 
             Reply  Mon Jun 20 11:11:20 2016, Steve, Configuration, CDS, GPS receiver not resetting properly 
                Reply  Mon Jun 20 11:19:41 2016, jamie, Configuration, CDS, GPS receiver not resetting properly 
                   Reply  Mon Jun 20 14:03:04 2016, jamie, Configuration, CDS, EndRun GPS receiver upgraded, fixed GPSreceiverWorking.jpg
          Reply  Wed Jun 15 10:19:10 2016, Steve, Configuration, CDS, GPS antennas... debugging 6x
Message ID: 12166     Entry time: Fri Jun 10 12:09:01 2016     In reply to: 12161     Reply to this: 12167   12182
Author: jamie 
Type: Configuration 
Category: CDS 
Subject: IRIG-B debugging 

Looks like we might have a problem with the IRIG-B output of the GPS receiver.

Rolf came over this morning to help debug the strange symmetricom driver behavior on fb1 with the new Spectracom card.  We restarted the machine againt and this time when we loaded the drive rit was clocking at a normal rate (second/second).  However, the overall GPS time was still wrong, showing a time in October from this year.

The IRIG-B122 output is supposed to encode the time of year via amplitude modulation of a 1kHz carrier.  The current time of year is:

controls@fb1:~ 0$ TZ=utc date +'%j day, %T'
162 day, 18:57:35
controls@fb1:~ 0$ 

The absolute year is not encoded, though, so the symmetricon driver has the year offset hard coded into the driver (yuck), to which it adds the time of year from the IRIG-B signal to get the correct GPS time.

However, loading the symmetricom module shows the following:

...
[ 1601.607403] Spectracom GPS card on bus 1; device 0
[ 1601.607408] TSYNC PIC BASE 0 address = fb500000
[ 1601.607429] Remapped 0xffffc90017012000
[ 1606.606164] TSYNC NOT receiving YEAR info, defaulting to by year patch
[ 1606.606168] date = 299 days 18:28:1161455320
[ 1606.606169] bcd time = 1161455320 sec  959 milliseconds 398 microseconds  959398630 nanosec
[ 1606.606171] Board sync = 1
[ 1606.616076] TSYNC NOT receiving YEAR info, defaulting to by year patch
[ 1606.616079] date = 299 days 18:28:1161455320
[ 1606.616080] bcd time = 1161455320 sec  969 milliseconds 331 microseconds  969331350 nanosec
[ 1606.616081] Board sync = 1
controls@fb1:~ 0$ 

Apparently the symmetricom driver thinks it's the 299nth day of the year, which of course corresponds to some time in october, which jives with the GPS time the driver is spitting out.

Rolf then noticed that the timing module in the VME crate in the adjacent rack, which also receives an IRIG-B signal from the distribution box, was also showing day 299 on it's front panel display. We checked and confirmed that the symmetricom card and the VME timing module both agree on the wrong time of year, strongly suggesting that the GPS receiver is outputing bogus data on it's IRIG-B output, even though it's showing the correct time on it's front panel.  We played around with setting in the GPS receiver to no avail.  Finally we rebooted the GPS receiver, but it seemed to come up with the same bogus IRIG-B output (again both symmetricom driver and VME timing module agree on the wrong day).

So maybe our GPS receiver is busted?  Not sure what to try now.

 

ELOG V3.1.3-