On 27/05/2013 04:52, Paul G wrote:
On Saturday, May 25, 2013 3:05:13 AM UTC-4, David Taylor wrote:
What happens with the fudge set to zero?
Please show the table for each machine.
Showing 192.168.0.2 and .244 with time1 = 0 as compared to the first post where
time1 was ~100 microsec.
These two have gigabit interfaces. 0.2 is driven by a Garmin 18x and 0.244 is
driven by a Firefly (I).
0.2
remote refid st t when poll reach delay offset jitter
==============================================================================
o127.127.22.0 .PPS. 0 l 1 8 377 0.000 -0.001 0.002
+192.168.0.244 .PPS. 1 u - 8 377 0.075 -0.128 0.001
*192.168.0.210 .GPS. 1 u 7 8 377 0.519 0.117 0.098
0.244
remote refid st t when poll reach delay offset jitter
==============================================================================
o127.127.22.0 .PPS. 0 l 5 8 377 0.000 0.000 0.002
+192.168.0.2 .PPS. 1 u 4 8 377 0.079 0.132 0.003
+192.168.0.210 .GPS. 1 u 4 8 377 0.547 0.253 0.135
*192.168.0.192 .PPS. 1 u 3 8 377 0.475 0.262 0.036
Well, that's interesting! Many thanks. 128/132 microseconds is way
more than I would expect a GPS/PPS signal to be off - it should be
nearer 1 microsecond (unless you're doing something unusual like a long
line driver, or triggering off the wrong edge of a 130 microsecond
pulse, perhaps?). I can't see a spec for the pulse width from the
Firefly, but I do see it has a programmeable offset. I presume that's
set to zero?
Purely for comparison, on the systems here:
- my FreeBSD/Intel Atom server sees my Windows XP system as -0.004, and
my Win-7 system as -0.077.
- my three Raspberry Pi cards see the FreeBSD server as -0.030 to +0.100.
- my three Raspberry Pi cards see the Windows XP system as -0.040 to +
0.070, and my Win-7 system as -0.020 to + 0.130. One RasPi is connected
via Wi-Fi.
All of these are triggered from PPS signals which are well within 0.1
microseconds of each other when viewed on a digital storage scope. The
18x LVC signal to the FreeBSD node may be a little delayed because of
the way it's being processed. I guess it says something about the
internal delays in each PC, and perhaps something about the difference
between network and serial/DCD processing. Each PC's clock is /not/
being set to UTC, but to some offset from UTC, which NTP measures as
near zero.
Cheers,
David
--
Cheers,
David
Web: http://www.satsignal.eu
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