Re: NTP with a Serial PPS
- From: "Dennis Hilberg, Jr." <timekeeper@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 26 Sep 2007 09:39:11 -0700
Elio wrote:
Hi to all,
my name is Elio and I work in an Italian seat of the Nokia Siemens Network.
We're making some tests on NTP and we want to use a GPS as a Primary
Ref. Clock in order to synchronize an NTP Stratum 1 PC.
The starting point was Philip M. White documentation called "Using a
Garmin GPS 18 LVC as NTP stratum-0 on Linux 2.6".
The linux kernel that I use is a 2.6.18 version. I've downloaded the
last version of ntp (4.2.4p4) and configured it with the options
"--disable-all-clocks --disable-parse-clocks --enable-SHM
--enable-linuxcaps"; after I've compiled and installed it.
We've prepared also a cable that connect a PPS (TTL) signal from a BNC
connector with a RS-232 (with pins 1 DCD and 5 GND; we've also tried
with pins 9 and 5, modifying the driver shmpps).
The shmpps output seems to work, so "shmat ok" message appears and
also messages like these appears:
range:4-11 sys:1144597205/3044 ref:1144597205/0 prec: -11
range:5-12 sys:1144597219/3310 ref:1144597219/0 prec: -11
range:5-12 sys:1144597233/3546 ref:1144597233/0 prec: -12
range:3-10 sys:1144597247/3739 ref:1144597247/0 prec: -12
range:3-10 sys:1144597261/3954 ref:1144597261/0 prec: -13
range:5-12 sys:1144597275/4158 ref:1144597275/0 prec: -13
range:4-11 sys:1144597289/4042 ref:1144597289/0 prec: -14
range:2-9 sys:1144597303/3801 ref:1144597303/0 prec: -14
range:4-11 sys:1144597317/3619 ref:1144597317/0 prec: -14
but when I type the command "ntpd –p" the output is the following:
remote refid st t when poll reach delay offset ji
tter
=========================================================================
+mchm932a.siemen 139.25.228.79 3 u 15 16 377 31.581 -11.909 1.
941
+blns064x.bln.sb .GPS. 1 u - 16 377 45.182 0.229 0.
271
*mhpa6hjc.mch.sb .PPS. 1 u 4 16 377 32.284 0.522 0.
254
So not appears a line similar to :
*SHM(0) .PPS. 0 l 13 16 377 0.000 -0.015 0.
004
Are possible some configuration errors?
Have I omitted some steps in the settings or in the configuration?
Do you think that there could be an error only in the ntp configuration?
It follows my ntp.conf file content:
######## NTP.CONF FILE ##################
restrict default nomodify
restrict 127.0.0.1
fudge 127.127.28.0 refid PPS flag3 1
server 127.127.28.0 minpoll 4 prefer
#OUR INTERNAL NETWORK TIMESERVERS
server 139.25.228.82 minpoll 4 maxpoll 4
#Stratum 1 GPS
server 147.54.45.7 minpoll 4 maxpoll 4
#Server Stratum1 CESIUM
server 139.25.66.22 minpoll 4 maxpoll 4
driftfile /var/lib/ntp/drift
broadcastdelay 0.008
keys /etc/ntp/keys # this file is empty
############## ENDOFFILE ################
Sure of a rapid reply…
Thanks in advance.
Best Regards,
Hi,
I run shmpps on Linux with a Garmin GPS 18 LVC, with no problems.
You might try putting the fudge line below the server line as that could be what's preventing the SHM peer from showing up in the 'ntpq -p' banner. I'm not an expert, but that's about the only difference between your shmpps setup and mine.
######## NTP.CONF FILE ##################
restrict default nomodify
restrict 127.0.0.1
server 127.127.28.0 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.0 refid PPS flag3 1
#OUR INTERNAL NETWORK TIMESERVERS
server 139.25.228.82 minpoll 4 maxpoll 4
#Stratum 1 GPS
server 147.54.45.7 minpoll 4 maxpoll 4
#Server Stratum1 CESIUM
server 139.25.66.22 minpoll 4 maxpoll 4
driftfile /var/lib/ntp/drift
broadcastdelay 0.008
keys /etc/ntp/keys # this file is empty
############## ENDOFFILE ################
Try that.
Regards,
--
Dennis Hilberg, Jr. timekeeper(at)dennishilberg(dot)com
NTP Server Information: http://saturn.dennishilberg.com/ntp.php
.
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- NTP with a Serial PPS
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