Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20
Hi, I decided to buy a Nanos G20. Not too expensive, real serial port, debian linux pre-installed. I don't want to sound harsh as the people from Nanos probably did their best to produce a good product, but for timekeeping it is totally crap and also useless. Well, unless I did something wrong. I recompiled the kernel to enable PPS support, installed gpsd and ntpd, configured at all and let it run for a while. allan deviation: http://keetweej.vanheusden.com/~folkert/nanosg20/allandev.png offset: http://keetweej.vanheusden.com/~folkert/nanosg20.png remote refid st t when poll reach delay offset jitter == x127.127.28.0.NMEA. 0 l3 16 3770.000 -994.05 7.857 x127.127.28.1.PPS.0 l7 16 3770.000 -250.13 572.812 +192.168.64.18 .PPS.1 u 66 128 3770.553 -0.055 0.033 *192.168.64.2.PPS.1 u 99 128 3770.237 -0.062 0.039 +192.168.64.168 .PPS.1 u 44 128 3770.646 -0.013 0.321 Folkert van Heusden -- MultiTail na wan makriki wrokosani fu tan luku den logfile nanga san den commando spiti puru. Piki puru spesrutu sani, wroko nanga difrenti kroru, tya kon makandra, nanga wan lo moro. http://www.vanheusden.com/multitail/ -- Phone: +31-6-41278122, PGP-key: 1F28D8AE, www.vanheusden.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20
folk...@vanheusden.com said: remote refid st t when poll reach delay offset jitter == x127.127.28.0.NMEA. 0 l3 16 3770.000 -994.05 7.857 x127.127.28.1.PPS.0 l7 16 3770.000 -250.13 572.812 +192.168.64.18 .PPS.1 u 66 128 3770.553 -0.055 0.033 *192.168.64.2.PPS.1 u 99 128 3770.237 -0.062 0.039 +192.168.64.168 .PPS.1 u 44 128 3770.646 -0.013 0.321 Something is broken. What NMEA device are you using? Why are you using gpsd rather than ntpd's NMEA driver? It looks like the NMEA side it is off by a second. Some devices do that. You can fix that with some fudging. The PPS stuff is off by 250 ms. Are you using the wrong edge? (Got a scope handy?) -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20
Hi, I decided to buy a Nanos G20. Not too expensive, real serial port, debian linux pre-installed. I don't want to sound harsh as the people from Nanos probably did their best to produce a good product, but for timekeeping it is totally crap and also useless. Well, unless I did something wrong. I recompiled the kernel to enable PPS support, installed gpsd and ntpd, configured at all and let it run for a while. allan deviation: http://keetweej.vanheusden.com/~folkert/nanosg20/allandev.png offset: http://keetweej.vanheusden.com/~folkert/nanosg20.png remote refid st t when poll reach delay offset jitter == x127.127.28.0.NMEA. 0 l3 16 3770.000 -994.05 7.857 x127.127.28.1.PPS.0 l7 16 3770.000 -250.13 572.812 +192.168.64.18 .PPS.1 u 66 128 3770.553 -0.055 0.033 *192.168.64.2.PPS.1 u 99 128 3770.237 -0.062 0.039 +192.168.64.168 .PPS.1 u 44 128 3770.646 -0.013 0.321 Folkert van Heusden == Folkert, Thanks for your graphs, but what are the Y-axis units! Inn your billboard above, the PPS looks to be on the wrong edge - perhaps the pulse is 250 ms wide and you are syncing to the trailing edge and not the leading. Can you check that out? I recall that it's the positive going transition on the DCD connection which needs to be on the exact second. I think you are using the Garmin GPS 18x LVC. There was a firmware update which ensured that the serial adta arrived /before/ the /next/ second edge rather than after it. Ensure your firmware is 3.70 or later. See: http://www.satsignal.eu/ntp/Garmin-GSP18x-LVC-firmware-issue.htm I see that 3.80 is now out, but I think I am still on 3.70. Hope that helps Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20
> folk...@vanheusden.com said:
> remote refid st t when poll reach delay offset jitter
> ==
> x127.127.28.0.NMEA. 0 l3 16 3770.000 -994.05 7.857
> x127.127.28.1.PPS.0 l7 16 3770.000 -250.13 572.812
> +192.168.64.18 .PPS.1 u 66 128 3770.553 -0.055 0.033
> *192.168.64.2.PPS.1 u 99 128 3770.237 -0.062 0.039
> +192.168.64.168 .PPS.1 u 44 128 3770.646 -0.013 0.321
>
> Something is broken. What NMEA device are you using? Why are you using gpsd
It is a garmin 18x lvc.
> rather than ntpd's NMEA driver?
Oh for convenience. I need to patch ntpd to use linux pps (afaik) and on
other systems I successfully run gpsd with ntpd (read: low jitter).
> It looks like the NMEA side it is off by a second. Some devices do that.
> You can fix that with some fudging.
Yes, I'm not so worried about the nmea part, I might even decide to
remove it from the configuration. What I mean is: if I set the clock to
the current time, than it is only a matter of keeping it at that with
the pps.
> The PPS stuff is off by 250 ms. Are you using the wrong edge? (Got a scope
> handy?)
Well, the offset is not constant. If you look at
http://keetweej.vanheusden.com/~folkert/nanosg20.png you see it is
between 0 and -1ms. I now notice that it is not random-ish but consists
of a few specific values:
folkert@belle:~$ cat peerstats | grep 127.127.28.1 | awk '{ print $5; }' | cut
-c 1-6 | sort | uniq -c | sort -rn
503 -0.874
497 -0.875
486 -0.999
467 -1.000
365 -0.249
332 -0.250
201 -0.857
188 -0.125
184 -0.142
140 -0.124
131 -0.000
113 0.
108 -0.166
24 -0.833
5 -0.200
2 -0.856
2 -0.799
2 -0.199
1 -0.167
1 -0.143
1 0.0002
1 0.0001
This is with 3754 lines.
If I clean it a little:
1000x -0.8745
953x -0.9995
697x -0.2495
328x -0.1245
and so on.
Folkert van Heusden
--
MultiTail är ett flexibel redskap för att följa en eller flera logfiler, utföra
kommandon, filtrera, färglägga, sammanfoga, o.s.v...
--
Phone: +31-6-41278122, PGP-key: 1F28D8AE, www.vanheusden.com
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20
> Thanks for your graphs, but what are the Y-axis units! http://keetweej.vanheusden.com/~folkert/nanosg20.png is in ms and not the delay, the offset instead. > Inn your billboard above, the PPS looks to be on the wrong edge - > perhaps the pulse is 250 ms wide and you are syncing to the trailing > edge and not the leading. well the offset is not constant. Now it is even 1 second: remote refid st t when poll reach delay offset jitter == x127.127.28.0.NMEA. 0 l5 16 3770.000 -1002.1 0.096 *127.127.28.1.PPS.0 l9 16 3770.000 -1000.2 394.379 +192.168.64.18 .PPS.1 u 64 64 3770.548 -0.360 3.083 +192.168.64.2.PPS.1 u 108 128 3770.251 -1.128 0.918 -192.168.64.168 .PPS.1 u 34 64 3771.153 -0.755 3.958 > Can you check that out? I recall that I can but I think (open for telling me I'm wrong) the primary problem is with the offset jumping all over the place: see my mail a couple of minutes ago. > it's the positive going transition on the DCD connection which needs > to be on the exact second. I think you are using the Garmin GPS > 18x LVC. There was a firmware update which ensured that the serial > adta arrived /before/ the /next/ second edge rather than after it. > Ensure your firmware is 3.70 or later. See: > http://www.satsignal.eu/ntp/Garmin-GSP18x-LVC-firmware-issue.htm > I see that 3.80 is now out, but I think I am still on 3.70. I'll have a look at it this weekend. Folkert van Heusden -- Multitail es una herramienta flexible que permite visualizar los "log file" y seguir la ejecución de comandos. Permite filtrar, añadir colores, combinar archivos, la visualización de diferencias (diff- view), etc. http://www.vanheusden.com/multitail/ -- Phone: +31-6-41278122, PGP-key: 1F28D8AE, www.vanheusden.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20
The computer itself and the NTP installation are OK because we can see it syncing to other NTP servers. Likely you have a problem in the way the GPS using is connected. Some common errors is an inverted PPS, just flip it ad see if you gets better, it is really hard to see a 1Hz signal on a scope. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20
On Wed, Jul 3, 2013 at 4:14 PM, folkert wrote: > > > Oh for convenience. I need to patch ntpd to use linux pps (afaik) and on > other systems I successfully run gpsd with ntpd (read: low jitter). Using gpsd with ntpd reduces the jitter versus just using ntpd by itself? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20
> It is a garmin 18x lvc. That's pretty vanilla. It really should work. I won't be surprised if the NMEA is off by hundreds of ms and/or has 100 ms of wander, but the PPS should work. Would you please try ntpd's NMEA driver, preferably from the latest ntp-dev http://support.ntp.org/bin/view/Main/SoftwareDownloads The PPS code used by ntpd is different from gpsd. If that doesn't work we should try to fix it. >> rather than ntpd's NMEA driver? > Oh for convenience. I need to patch ntpd to use linux > pps (afaik) and on other systems I successfully run gpsd > with ntpd (read: low jitter). Were any of those systems ARM? - One possibility is that the CPU is getting turned off when idle to save power. If that includes the stuff normally used for timekeeping, things could get screwed up when it gets turned back on. It has to reset the time, probably getting it from the RTC. Can you measure the power when idle? (kill off as much as possible, things like ntpd) If that's suspiciously low that might be the problem. Can you keep it busy? If nothing else, "while true; do true; done" -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20
You could also try questi...@lists.ntp.org. The developers etc hang out on that list. There are a lot of helpful experts on NTP there. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray Sent: Thursday, 4 July 2013 8:34 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20 > It is a garmin 18x lvc. That's pretty vanilla. It really should work. I won't be surprised if the NMEA is off by hundreds of ms and/or has 100 ms of wander, but the PPS should work. Would you please try ntpd's NMEA driver, preferably from the latest ntp-dev http://support.ntp.org/bin/view/Main/SoftwareDownloads The PPS code used by ntpd is different from gpsd. If that doesn't work we should try to fix it. >> rather than ntpd's NMEA driver? > Oh for convenience. I need to patch ntpd to use linux pps (afaik) and > on other systems I successfully run gpsd with ntpd (read: low jitter). Were any of those systems ARM? - One possibility is that the CPU is getting turned off when idle to save power. If that includes the stuff normally used for timekeeping, things could get screwed up when it gets turned back on. It has to reset the time, probably getting it from the RTC. Can you measure the power when idle? (kill off as much as possible, things like ntpd) If that's suspiciously low that might be the problem. Can you keep it busy? If nothing else, "while true; do true; done" -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20
> > > One possibility is that the CPU is getting turned off when idle to save > power. If that includes the stuff normally used for timekeeping, things > could get screwed up when it gets turned back on. It has to reset the > time, probably getting it from the RTC. > I don't think this is the case. Look at how well the system to sync'd with other NTP servers. It is only the local GPS ref. clocks that are not doing well. Also you might check the NMEA output by some other means, some Garmin units are really bad. If you can turn off all the un-needed NMEA sentences it might help. Simply watching the NMEA output in a terminal window is a good enough check. You can see by eye if there is a one second error -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20
> > Oh for convenience. I need to patch ntpd to use linux pps (afaik) and on > > other systems I successfully run gpsd with ntpd (read: low jitter). > > Using gpsd with ntpd reduces the jitter versus just using ntpd by itself? No I meant that running that combination is successfully because I see low jitter. Folkert van Heusden -- Multitail est un outil permettant la visualisation de fichiers de journalisation et/ou le suivi de l'exécution de commandes. Filtrage, mise en couleur de mot-clé, fusions, visualisation de différences (diff-view), etc. http://www.vanheusden.com/multitail/ -- Phone: +31-6-41278122, PGP-key: 1F28D8AE, www.vanheusden.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
