[ntp:questions] fudge time1 for gps-18x-LVC?
David J Taylor
david-taylor at blueyonder.delete-this-bit.and-this-part.co.uk.invalid
Sun Feb 7 09:35:26 UTC 2010
"David Lord" <snews at lordynet.org> wrote in message
news:7t6oaaFul7U1 at mid.individual.net...
[]
> Now NMEA(0) 92u/6u and PPS(0) 75u/2u, 60 minutes after ntpd restarted.
>
> Config:
> pps to lpt0
> pps to serial dcd
> lpt0 at ppbus
> pps0 at ppbus
> crw-r--r-- 1 root wheel 164, 0 Feb 7 01:47 pps0
> server 127.127.20.0 mode 1 prefer minpoll 6 maxpoll 8
> server 127.127.22.0 minpoll 4 maxpoll 6
>
> 7 Feb 01:46:18 ntpd exiting on signal 15
> 7 Feb 01:47:38 clock PPS(0) event 'clk_noreply' (0x01)
> 7 Feb 01:51:58 synchronized to 192.168.59.60, stratum 2
> 7 Feb 01:51:58 kernel time sync status change
> 0x2001<PLL,NANO,MODE=0x0=PLL,CLK=0x0=A>
> 7 Feb 01:51:59 synchronized to GPS_NMEA(0), stratum 0
> 7 Feb 01:53:09 synchronized to PPS(0), stratum 0
>
> remote refid st t when poll reach delay offset jitter
> ======================================================================
> +GPS_NMEA(0) .GPS. 0 l 19 64 377 0.000 -1.680 253.141
> oPPS(0) .PPS. 0 l 10 16 377 0.000 -1.652 0.150
> -k6x400 xxx.xxx.xxx.xxx 2 u 26 64 377 0.740 0.822 0.778
> +me6000g .PPS. 1 u 21 64 377 1.767 -0.439 0.309
> -p4x2400c xxx.xxx.xxx.xxx 2 u 22 64 377 1.893 0.611 0.520
David,
Thanks for the details. My (rather limited) understanding was that the
atom driver was simply a filter on an existing PPS signal, and therefore
you would need a driver which knew about the LPT port and could detect and
use its PPS signal. Which driver does that I don't know, as I've never
used one.
> Now NMEA(0) 92u/6u and PPS(0) 75u/2u, 60 minutes after ntpd restarted.
Are these jitter/offset figures? Do I gather that the 253 milliseconds
NMEA jitter was at the start, and it's now 6 microseconds? Why so bad at
the start, or was that simply the first reading? But it can't be the
first reading as it shows Atom sync, which was 7 minutes after the start.
The "billboard" NMEA jitter figure puzzles me!
Cheers,
David
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