David J Taylor wrote:
"David Lord" <[email protected]> wrote in message
news:[email protected]...
[]
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!
offset/jitter for NMEA now at 10u/2u and for PPS at 7u/2u
Downside of not having fudge is first few NMEA offsets are 350ms
until the NMEA driver sorts out its own handling of pps. As soon as
offset shifts to a few ms or less jitter then rockets to near 350ms
and works down from there fairly quickly.
It's probably worth trying with the fudge time1 in place as that
might just improve startup.
....
xGPS_NMEA(0) Offset 650ms
I'm sure that indicates it doesn't work.
....
*GPS_NMEA(0) reach 377 Offset 650.167 jitter 0.305
and servers right now all just been marked rejected
GPS_NMEA(0) reach 0
serv2 .PPSa. reach 0 Offset -649.27
Now back to config without fudge
Cleanest but not fastest startup is with NMEA fudged correct
amount without serial DCD, and using only ATOM driver for
accuracy. That still gives large startup jitter from NMEA
sentences coming in.
These are VIA C3 mini epia me6000 and me6000g motherboards
and I get impression they don't have good quality clock
oscillators.
David
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