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Re: [gpsd-dev] GPS week wraparound
From: |
Andy Walls |
Subject: |
Re: [gpsd-dev] GPS week wraparound |
Date: |
Fri, 27 Sep 2013 09:01:46 -0400 |
Hi:
On Fri, 2013-09-27 at 10:08 +0000, Harlan Stenn wrote:
> --
> "Eric S. Raymond" writes:
> > Harlan Stenn <address@hidden>:
> > > OK. Does GPSD address this problem? I'm thinking that the NTP GPS
> > > refclocks should handle this the same way GPSD does.
> >
> > From the header of timebase.c:
[snip]
> > 5) Another source *may* be available - the GPS leap second count, if we can
> > get the device to report it. The latter is not a given; SiRFs before
> > firmware rev 2.3.2 don't report it unless special subframe data reporting
> > is enabled, which requires 38400bps. Evermore GPSes can't be made to
> > report it at all.
This is not reliable. I have a GPS unit that reports the leap second
count when queried.
But without battery hold-up, the device steps time sometime *after*
start-up to insert another leap second after the GPS almanac is loaded:
After startup:
UTC Correction Query: $PMTK457
UTC Correction Response: $PMTK557,15.0*03
After a second is repeated/inserted
UTC Correction Query: $PMTK457
UTC Correction Response: $PMTK557,16.0*00
Before the almanac is received, the device is working with
the leap-seconds correction before the June 30,2012 leap-
second.
It is obvious the GPS unit has an initial, hard-coded leap second count
that is out of date.
Harlan:
On a related note, what is the best way to have NTPD accept the jump in
time and not mark my GPS clock (and PPS source) as false tickers?
Regards,
Andy
- [gpsd-dev] GPS week wraparound, Harlan Stenn, 2013/09/27
- Re: [gpsd-dev] GPS week wraparound, Eric S. Raymond, 2013/09/27
- Re: [gpsd-dev] GPS week wraparound, Harlan Stenn, 2013/09/27
- Re: [gpsd-dev] GPS week wraparound, Eric S. Raymond, 2013/09/27
- Re: [gpsd-dev] GPS week wraparound, Harlan Stenn, 2013/09/27
- Re: [gpsd-dev] GPS week wraparound,
Andy Walls <=
- Re: [gpsd-dev] GPS week wraparound, Hal Murray, 2013/09/27
- Re: [gpsd-dev] GPS week wraparound, Andy Walls, 2013/09/27
- Re: [gpsd-dev] GPS week wraparound, Magnus Danielson, 2013/09/27
- Re: [gpsd-dev] GPS week wraparound, Hal Murray, 2013/09/27
- Re: [gpsd-dev] GPS week wraparound, Magnus Danielson, 2013/09/28
- Re: [gpsd-dev] GPS week wraparound, Eric S. Raymond, 2013/09/27
- Re: [gpsd-dev] GPS week wraparound, Harlan Stenn, 2013/09/28
- Re: [gpsd-dev] GPS week wraparound, Eric S. Raymond, 2013/09/27
- Re: [gpsd-dev] GPS week wraparound, Hal Murray, 2013/09/27
- Re: [gpsd-dev] GPS week wraparound, Eric S. Raymond, 2013/09/27