[ntp:questions] PPS as a falseticker!!!
valizadeh65 at gmail.com
valizadeh65 at gmail.com
Wed Aug 27 09:48:48 UTC 2014
Following my previous post.
https://groups.google.com/forum/#!topic/comp.protocols.time.ntp/aGjxoHvj0QA
I not sure, how should I write the ntp.conf file to achieve the maximum accuracy using pps.
i don't know if the ntpd use the pps or not in my case!
Sometimes it is recognized as a "falseticker" (x) and sometimes it is OK(o) !!!
I tested different ntp.conf and here are some results (ntp.conf and ntpq-p):
#TEST:1
----- ntp.conf-------
server 127.127.22.1 minpoll 4 #PPS
server 127.127.20.1 prefer minpoll 4 mode 16 #GPS
fudge 127.127.20.1 flag1 1 flag3 1
-----
GPS on COM port (PPS connected to DCD pin)
remote refid st t when poll reach delay offset jitter
==============================================================================
xPPS(1) .PPS. 0 l 3 16 377 0.000 30.681 29.011
oGPS_NMEA(1) .GPS. 0 l 2 16 377 0.000 29.964 29.404
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
#TEST:2
----- ntp.conf-------
#server 127.127.22.1 minpoll 4 #PPS
server 127.127.20.1 prefer minpoll 4 mode 16 #GPS
fudge 127.127.20.1 flag1 1 flag3 1
GPS on COM port (PPS connected to DCD pin)
remote refid st t when poll reach delay offset jitter
==============================================================================
oGPS_NMEA(1) .GPS. 0 l - 16 377 0.000 -1.004 0.316
Questions:
1- Shall the "server 127.127.22.1 minpoll 4 " be inevitably present in ntp.conf?(test1) or can driver 20 use the PPS individually by enabling flag1 1(test2)
2- How can kernel pps discipline affect the time sync accuracy? What do you recommend? Enable or disable it?
3- What are the best choices for flag 1, flag 2, flag 3 in driver20 and 22?
4- How may I select the best time1, time 2 in driver 20 and 22? Shall I use the oscilloscope? What should I measure?
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