Re: [chrony-users] Not getting time from gpsd

On Mon, Aug 15, 2016 at 10:18 AM, Bill Unruh <unruh@xxxxxxxxxxxxxx> wrote:

On Mon, 15 Aug 2016, Chris Greenman wrote:

No. We're just fine tuning the refclock line in chrony.conf. I don't really
experience huge jumps. It might fall behind during a reboot because the pi doesn't
have an RTC but rather it saves time on shutdown and restores on boot.

Ah sorry. they yes, during that time period gps settled down to being out about 10ms
which is well within your requirements. Unrotunately, nmea is not the most
stable of references. Thus if for some reason your gps puck becomes busy for
some reason, (moving the computer, something happens with the gps
constellation,...) that offset could change, but certainly not by a second.
The handling of leap seconds by your puck could be an issue. Not sure how it
handles that. But at worst it would mean that some midnight (UTC) at the end
of Dec or Jun, the clock would suddenly be out by a second, and would slowly
(well not that slowly with chrony) drift its way back into sync.

Really my only goal is to have somewhat accurate (less than a second) time whether I
have internet or not. We've already achieved this, now it's just a matter of
making sure GPS doesn't clobber ntp and vice versa.

Not sure what you mean by "ntp".

On Aug 14, 2016 7:24 PM, "Bill Unruh" <unruh@xxxxxxxxxxxxxx> wrote:
Is this supposed to be at a time when your system suddenly looses track
of the
time and jumps by hours or days? I see nothing in the gps signal that
indicates anything like that.

If it is supposed to be at the begining of this sample, please give a
sample
which spans across, not begins at, one of those weirdnesses.

Note also that probably a copy of the measurements and the refclock logs
ove
onw of those times might be more illuminating. Statistics is rather
processed
already.

William G. Unruh __| Canadian Institute for|____ Tel: +1(604)822-3273
Physics&Astronomy _|___ Advanced Research _|____ Fax: +1(604)822-5324
UBC, Vancouver,BC _|_ Program in Cosmology |____ unruh@xxxxxxxxxxxxxx
Canada V6T 1Z1 ____|____ and Gravity ______|_ www.theory.physics.ubc.ca/

On Sun, 14 Aug 2016, Chris Greenman wrote:

Ok I grabbed a sample of the clock statistics.

On Fri, Aug 12, 2016 at 2:53 PM, Bill Unruh
<unruh@xxxxxxxxxxxxxx> wrote:
On Fri, 12 Aug 2016, Chris Greenman wrote:

it's a usb puck. so no. Actually I haven't
actually looked but
typical USB is +5v data+ data- and gnd. As
far as I know the only place the pps signal is
available is inside the
puck between the GPS module and the usb
interface.

Well, usb serial immitatiors can also immitate the
control lines from a serial
line. Thus one of the usb packets can be a simlation
of the PPS signalalong
the appropriate serial line. But those are likely to
have far worse behaviour
than the actual lines.
It might however be better than the data phrases
usually coming along the
serial line.

like I said I COULD crack it open and run a new
cable that included
the pps line.

On Fri, Aug 12, 2016 at 2:24 PM, Bill Unruh
<unruh@xxxxxxxxxxxxxx>
wrote:

William G. Unruh __| Canadian Institute
for|____ Tel:
+1(604)822-3273
Physics&Astronomy _|___ Advanced Research
_|____ Fax:
+1(604)822-5324
UBC, Vancouver,BC _|_ Program in Cosmology
|____
unruh@xxxxxxxxxxxxxx
Canada V6T 1Z1 ____|____ and Gravity
______|_
www.theory.physics.ubc.ca/

On Fri, 12 Aug 2016, Chris Greenman wrote:

I CAN hook it up for PPS but it will
require cracking open
the puck and it's not that
crucial for my use
anyway.

Isn't there an output line from the puck
which carries the PPS
signal?