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" <un...@physics.ubc.ca> 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 |____ un...@physics.ubc.ca
      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
            <un...@physics.ubc.ca> 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
            <un...@physics.ubc.ca>
                        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
            |____
                        un...@physics.ubc.ca
                              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?






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