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

[Rich Wales]

    Hi.  I have two Garmin 18X LVC units -- one bought in 2009, the
    other purchased about a month ago.
    
    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.) 
    I've never made any attempt to flash it with newer firmware (I'm not
    even sure if that's possible).
    
    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.
    
    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.
    
    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?
    
    Rich Wales
    address@hidden