Re: [gpsd-users] Garmin 18X LVC and upcoming week rollover

[Gary E. Miller]

Yo Rich!

On Sat, 30 Nov 2019 17:01:42 -0800
Rich Wales <address@hidden> wrote:

> Hi.__ I have two Garmin 18X LVC units -- one bought in 2009, the other
> purchased about a month ago.

Ouch.  Those hage been obsolete for years.

> The brand new Garmin works just fine; I'm going to talk here about the
> older unit.__ It's connected to a Linux system via a serial port on the
> motherboard.__ (Ubuntu 18.04.3 LTS, gpsd 3.17, ntpsec 1.1.0.)

3.17 has known bugs.  It is from before the last GPS Roll Over Event.

>__ I've
> never made any attempt to flash it with newer firmware (I'm not even
> sure if that's possible).

You did no mention your Garmin firmware versions.  You need 4.x to
fix the date bugs.

> Five days ago (around 2019-11-26T00:00Z), this 10-year-old GPS jumped
> back to 2000-04-11 -- evidently the WNRO problem finally struck.

Yup.

> I was able to work around this problem by adding "time1 619315200" --
> that's the number of seconds in 1,024 weeks, of course__ -- to the
> "refclock" line for the GPS in my ntp.conf file and restarting
> ntpsec. I's working just fine now as a time reference; if I use cgps
> to examine the state of the GPS, the date/time is all wrong, but I
> can live with that.

Not all wrong, off by 619315200 seconds.

> I understand some code in timebase.c is supposed to catch the rollover
> problem and compensate for it, but this clearly wasn't happening in my
> case.__ Any thoughts?

Try the code in git head.

Or get a modern GPS.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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