RE: FreeBSD Garmin 18x LVC receiver - precision -20

[Philippe Maechler]

Hello Gary and List

>> While googling I saw other outputs with a precision of -3
>> and the like.

> -3 is the assumed precision for time from the serial stream.

>> So I tought it has something to do with “how accurate
>> the position is”

> Your thought is correct.  PPS is kinda sorta accurate to -20.

>> Since I had the impression that the receiver is not “precise” I debug
>> ntpd further😊

> What do you think you need to debug?

Oh boy, I should *not* attend online meetings and answer emails at the same time^^

I’meant that “Since I had the impression that the receiver is not precise, I “did not* look into the ntpd configuration

> I guess you are using NTP Classic, not NTPsec.  With NTPsec a peer
> and a server are the same thing.

Yes I’m running the «default” ntpd from base freebsd. Now, after reading lots of articles and how-to’s I’m thinking about switching to chrony or NTPsec…

>> server 127.127.20.0 mode 1 prefer
>> fudge  127.127.20.0 time1 0.000 refid PPS

> That is configuring ntp direct to the serial port.  gpsd is not being
> used by ntpd.  But if gpsd is connected to the receiver, then ntpd can
> not also directly read the receiver.  This is not per the gpsd howto's as
> it does not use gpsd!

The system is now working. This comment made me thinking about using the receiver without gpsd and after a bit of googling I found *the* list of all the 127.127.t addresses available. Guess this one was the missing part on my side.

The system is now working

# ntpq -p

     remote           refid      st t when poll reach   delay   offset  jitter

==============================================================================

xSHM(0)          .NMEA.           0 l   15   16  377    0.000  -376.46   3.917

*SHM(1)          .PPS.            0 l   13   16  377    0.000   -0.252   0.085

-metasntp11.admi .MRS.            1 u   33   64    7    3.508   -0.065   0.171

-metasntp13.admi .MRS.            1 u   33   64    7    3.555   -0.143   0.413

-ntps1-0.eecsit. .PPS.            1 u   33   64    7   22.126   -0.753   0.238

+time0.swissix.c .MRS.            1 u   33   64    7    1.045   -0.416   0.080

+tick.as34288.ne .MRS.            1 u   36   64    7    1.086   -0.280   0.193

-ntp.freestone.n .PPS.            1 u   31   64    7    9.615   -0.780   0.196

 s1-ntp2.glattne 85.158.27.31     2 s   36   64    6    0.350   -0.410   0.052

 

# ntptime

ntp_gettime() returns code 0 (OK)

  time e33a8c10.f17d49d8  Wed, Oct 21 2020 12:29:36.943, (.943318352),

  maximum error 6000 us, estimated error 2 us, TAI offset 37

ntp_adjtime() returns code 0 (OK)

  modes 0x0 (),

  offset -1.563 us, frequency 16.392 ppm, interval 1 s,

  maximum error 6000 us, estimated error 2 us,

  status 0x2001 (PLL,NANO),

  time constant 4, precision 0.001 us, tolerance 496 ppm,

 

 

 And when I query from another host (client of this server)

 pmaechler@NTP1-1:~ % ntpq -p

     remote           refid      st t when poll reach   delay   offset  jitter

==============================================================================

*s1-ntp1.glattne .PPS.            1 u   29  256  377    0.388   +0.571   0.129

+s1-ntp2.glattne 85.158.27.31     2 u  211  256  377    0.465   +0.275   0.143

pmaechler@NTP1-1:~ %

Now comes the part where I fine tune the system 😊 If any questions arise, I’ll come back to a list, but I guess then I’m better suited on the ntpd list and not gpsd 😊

Thank you Gary for your support

/BR

Philippe