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Re: [gpsd-users] Garmin 18X-5Hz

From: Alexander Carver
Subject: Re: [gpsd-users] Garmin 18X-5Hz
Date: Mon, 15 Aug 2016 11:57:37 -0700
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0

On 2016-08-15 11:12, Gary E. Miller wrote:
> Yo Alexander!
> On Mon, 15 Aug 2016 08:10:09 -0700
> Alexander Carver <address@hidden> wrote:
>>> I use 28.  gpsd does all the work and hands the time corrections to
>>> ntpd to deal with.  That is how the gpsd time server howto does it,
>>> as well as the in progress NTPsec RasPi howto.  
>> I find this interesting because on four different hardware platforms
>> using different OSes and different GPS receivers I can not get gpsd's
>> PPS SHM output to behave.
> Many many people do this just fine.  I have 8 boxes doing this now.  
> Eric has a simliar number.  We have a lot of beta testers doing
> similar.  There are zero open bugs on anything like this.  I can provide
> many graphs showing it works fine, and has for many years.

Yes, I hear this but I have not been able to replicate the results.

>>  It consistently feeds awful time to ntpd
>> and, in the end, I use the ntpd PPS driver (22) to keep things under
>> control.
> Well, since that driver is deprecated, maybe we need to find out how to
> fix your installations?
>> I feed the coarse clock into ntpd via gpsd (so the GPS
>> receiver data can be monitored or shared with other applications) but
>> PPS via SHM is terrible (offset in milliseconds and jitter also in
>> milliseconds, using Driver 22, offset and jitter are single digit
>> microseconds.)
> Totally bizare.  Single digit microSeconds are the universal result.
> Are you sure your kernel PPS driver is installed correctly and seen by
> gpsd when it is built?

Yes, it's seen and installed correctly.  Works fine with Driver 22, it's
awful with gpsd.

>> Given that, I would really like to know how you have your whole system
>> configured because following any available recipe fails.  I see the
>> config in your link below and I've used that without success.
> My setup is documented in the gpsd time howto:
> www/gpsd-time-service-howto.txt
> And in the NTPsec Pi howto:
> If those do not work for anyone we would jump on it right away to get
> a fix.

I haven't tried it with a Raspberry Pi but I've tried it on several
normal machines (Intel motherboards, Sun, all with real serial ports)
using multiple OSes (Linux, Windows, Solaris, BSD) and several GPS
receivers with PPS outputs and they've all done miserably using SHM PPS.

>> In any event, is NTPsec a replacement or is this a fork of ntpd?
> Yes.

Is it an official replacement of the ntpd code base (i.e. ntpd's current
code will cease to exist and yours will replace it)?  I see no
documentation anywhere that suggests ntpd's code base is disappearing.

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