[ntp:questions] Re: Garmin 18lvc working (finally!)

flyfatpig at gmail.com flyfatpig at gmail.com
Thu Mar 30 03:38:01 UTC 2006


The configure as below:

# cat ntp.conf
#
#
driftfile /var/log/drift                    # remember the drift value
logfile /var/log/ntpd                                       # log file
#
# Enable kernel PPS
#
#enable pps
#
# pps pps_device [assert|clear] [hardpps]
# assert means use the rising edge of the PPS signal
# clear means use the falling edge of PPS signal
# In the the TAC2/(Oncore UT+) the assert/clear should
# be specified in the ntp.oncore0 configuration file.
# Warning: The pps option line MUST precede any server lines
#
#pps /dev/oncore.pps.0 clear hardpps
#
# Use GPS/TAC2/Oncore clock
tinker panic 0
server 127.127.30.0 prefer minpoll 4 maxpoll 4
fudge 127.127.30.0 refid GPS flag3 1 flag2 1 time1 -0.2
#
# Servers for backup. Using more than one could cause problems.
#
#server 208.184.49.9    # nist1-ny.glassey.com NYC local server
#server clock.cuhk.edu.hk
#server 128.118.46.3    # otc1.psu.edu
#server 140.142.16.34   # bigben.cac.washington.edu
#server 128.252.19.1    # navobs1.wustl.edu
#server 18.145.0.30             # navobs1.mit.edu
#server 129.6.15.29             # time-b.nist.gov
#
auth no


# cat ntp.oncore0
#
# Warning:
#
#               If you set MODE to 3 or 4 you will lose the almanac and
you will
#               get many messages (if you are in debug mode) like:
"waiting for almanac".
#               Avoid this,     since it can take from 15-30Mins to
re-acquire almanac
#               from the satellites. It you don't have a UT+ with
battery backup,
#               you have no choice but MODE 3,4.
#               Also, if this is the first time that the Oncore will be
set up, you should do
#               MODE 3,4 to set everything.
#               Read the NTP Oncore setup notes on: www.darksmile.net
#
# MODE {0|1|2|3|4}
# MODE 0 Means thet the Oncore has been pre-initialized
#
# For MODE 1,3 Specify the following or MODE will revert to 2,4
#
# LONG DDD MMM SSS.sss
# LAT  DDD MMM SSS.sss
# HT   nnn {FT|M}               # Note that this is the "GPS" Height
not "MSL"
# DELAY nn.n ns
MODE 2
#
#
# DELAY = Antenna Cable_Delay + Other_Cable_Delay +
Internal_Receiver_Delay + Intentional_Extra_Delay_Early_Offset
#
#DELAY 168.9 ns
#
# OFFSET nnn NS
#
# Specifying ASSERT or CLEAR here will override the option if it was
# specified in ntp.conf
# ASSERT | CLEAR
#ASSERT
#CLEAR
# add by lxh-20030806
#HARDPPS

#
# Enable SHmem interface
#
SHMEM /var/log/ONCORE
#
# Avoid Posn2D/3D if possible, since you WILL lose timing info.
# Note: The number specified after Posn3D will only work if
# you have the darksmile.net modifications to refclock_oncore.c
#
#Posn3D 600
#
#
# CHAN {6|8|12}
# TRAIM {YES|NO}
TRAIM YES

the result as below ,but why the rootdispersion is 440ms?and the time
server is not stable,it will not sync GPS about every 15min.

ntpq> pe
     remote           refid      st t when poll reach   delay   offset
jitter
==============================================================================
*GPS_ONCORE(0)   .GPS.            0 l    6   16  377    0.000  -200.00
 0.004
ntpq> rv
status=04a4 leap_none, sync_uhf_clock, 10 events, event_peer/strat_chg,
version="ntpd 4.2.0 at 1.1161-r Wed Feb 18 13:31:12 CST 2004 (5)",
processor="i586", system="Linux/2.4.20-NANO", leap=00, stratum=1,
precision=-18, rootdelay=0.000, rootdispersion=444.839, peer=58644,
refid=GPS, reftime=c7d5cb97.48282c6e  Thu, Mar 30 2006 11:14:31.281,
poll=4, clock=c7d5cba1.2bfcc9ea  Thu, Mar 30 2006 11:14:41.171,
state=3,
offset=0.000, frequency=-0.544, jitter=2.301, stability=161.969

when I use ntpdate query my time server and time.nist.gov ,the
difference is quit small.
but why the time server is not stable?
[root at gt4 lxh]# ntpdate -q 192.168.2.7
server 192.168.2.7, stratum 1, offset -0.225616, delay 0.02599
30 Mar 11:09:44 ntpdate[1368]: adjust time server 192.168.2.7 offset
-0.225616 sec
[root at gt4 lxh]# ntpdate -q time.nist.gov
server 192.43.244.18, stratum 1, offset -0.226255, delay 0.26195
30 Mar 11:09:49 ntpdate[1369]: adjust time server 192.43.244.18 offset
-0.226255 sec




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