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

From: Gary E. Miller
Subject: Re: [gpsd-users] Garmin 18X LVC and upcoming week rollover
Date: Wed, 4 Dec 2019 12:58:10 -0800

Yo Steve!

On Wed, 4 Dec 2019 14:00:13 -0600 (CST)
Steve Bourland <address@hidden> wrote:

>    Do you have recommendations for a replacement that will drop in as
> time keeping sources?

Nothing for an exact replacement.  The Garmin 18x LVC is an odd
beast.  Self contained, very waterproof, odd connector, PPS.

Something has to give if you lose the Garmin.

> I have 5 Garmins that have been keeping time
> for my offline networks for years and years, one has decided to be
> afflicted by the week rollover.

It all depends on the firmware date, which you still have not recovered.
The others may soon join the WKRO failed one.  Or not.

>  I don't really want to spend the
> time and energy to redo the wiring, just replace the receiver unit;
> so something with either the stupid Garmin testing connector (JST
> 06B-SRSS, I have boards with FETs on the PPS line that mate to this
> connector)

Not gonna happen.  No one ever thought the Garmin configuration was a
good one to copy.

> or DB-9 + USB for power, with the PPS on the DCD pin.

That is easy, with some DIY.  If you want cheap, then the deals change
every day.  Today, I see:

Start with a cheap NEO-M8N, with PPS, like this for $20:

Add in a TTL to RS-232 DB-9 converter, with DCD, like this for $3:

And an SMA antenna that does GALILEO, for $34:

If you want to also pick up GLONASS you need to be extra careful on the
antenna you buy.

Plus some jumpers to pull it all together.  Use an old USB cable for the

The common mistakes are:
    get a GNSS receiver that does not bing out PS.
    get a TTL to DB-9 that does not bring out DCD.
    get an antenna that does not to GALILEO.

>  I
> worked a bit a few months ago with a Beaglebone Black and Adafruit
> GPS hat/cape, but couldn't get the PPS to register (was planning to
> move to simple little time servers, vs. now the GPSes are feeding
> full PC based servers that have other tasks as well). Many thanks,

You read the Time Service Howto?  About using Raspberry Pi and a HAT?

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

            Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin

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