Steve Kostecke wrote:
On 2010-04-22, David Lord <[email protected]> wrote:
Chaofu Chen wrote:
Hi all. I want to build a NTP server but PPS doen't work for the time
being. Status bits from "ntptime" and "ntpdc -c kern" include PLL and
NANO, sometimes PPSTIME and PPSFREQ, but PPSSIGNAL never appears.
If you have a PPS signal on serial DCD, I'd suggest adding pps driver
"server 127.127.22.(n)" which requires /dev/pps(n)
The NMEA driver (127.127.20.X) will use the PPS signal if it is present
on the DCD pin.
http://doc.ntp.org/4.2.6/drivers/driver20.html provides set-up details.
You don't need the PPS driver (127.127.22.X).
With NetBSD-5, ntpd 4.2.4p6-o, gps18x-LVC, last year I seemed
to get lower offset and jitter from PPS driver that was from
just couple of days with each config. Having just rmc sentence
seemed to make a difference.
RMC-only Default
NMEA only 0.07 ms 0.12ms
+PPS type 22 0.002ms 0.004ms
Since then I've kept separate PPS driver
server 127.127.20.2 mode 1 minpoll 6 maxpoll 8 prefer
fudge 127.127.20.2 time1 0.100 refid GPSb
server 127.127.22.2 minpoll 4 maxpoll 4
fudge 127.127.22.2 flag2 1 flag3 1 refid PPSb
past 4 days from peer_summary
127.127.22.2
mean(ms) -0.000 0.000 0.000 0.000
rms(ms) 0.002 0.006 0.007 0.006
max(ms) 0.019 0.040 0.036 0.033
127.127.20.0
mean(ms) 0.002 0.003 0.003 0.003
rms(ms) 0.002 0.006 0.007 0.006
max(ms) 0.018 0.038 0.033 0.031
I'd guess large day/night temperature change is causing
higher rms/maximum offsets than normal.
David
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