[ntp:hackers] NTP Release Candidate 4.2.8p1-RC1 Released

Gary E. Miller gem at rellim.com
Wed Jan 28 22:25:56 UTC 2015

Yo All!

On Mon, 26 Jan 2015 16:44:51 -0800
"Gary E. Miller" <gem at rellim.com> wrote:

> On Sun, 25 Jan 2015 02:30:12 +0000
> NTP Public Services Project <webmaster at ntp.org> wrote:
> > NTP Release Candidate 4.2.8p1-RC1 is now available for download.
> I can not get the gpsdjson refclock to do anything.

Hal Murray has suggested this is an ntpd bug.  Any progress on this?


I looked at the GPSD_JSON code.  Two issues jump out at me.

1. The use of EPT to guess time precision is totally bogus.  It should
be removed.

    Time error in TPV is totally dominated by local effects such as
    serial port rate, NMEA variable sentence length, interrupt latency,

    Time error in PPS is totally dominated by port type (USB or direct serial)
    and by GPS model.

    I would suggest that precision be computed from observed jitter.

2. Flipping between TPV and PPS time is not a good idea.

    The precisions are wildly different, yet they will flip flop silently.

    It removes the ability for ntp.conf to prefer local PPS time but not
    prefer local TPV time.

    I would suggest that some way to separate TPV and PPS time is needed.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
	gem at rellim.com  Tel:+1(541)382-8588

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