[ntp:questions] Time synchronization

Dahal Runa rxd1271 at louisiana.edu
Wed Feb 11 17:37:35 UTC 2009


I would like to correct my previous data and send in more accurate
information. we are using RT3000(more accurate GPS receiver)and using ntp -q
program to query the output in both the nTP machine as well as the moxa board.
The following output were obtained. 
NTP data

    remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
xSHM(0)          .NMEA.           0 l    1   16    1    0.000    0.134   0.284
*SHM(1)          .PPS.            0 l    1   16  377    0.000    0.072   0.005

MOXA data
remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+SHM(0)          .NMEA.           0 l   11   16  377    0.000  -20.118   7.812
*SHM(1)          .PPS.            0 l   10   16  377    0.000  -16.061   7.812

On running the following command 

gpsd -n -D6 -N /dev/ttyM0

we  got the following log messages,but also the following data shows the
ntpshm_pps is not in locking range, we did have the pps signal in the locking
range later but still we are having the jitter in the moxa board as shown in
the data above. Is is normal for such MOXA board(UC-7112 plus) to receive such
high offset values? Can we replace it in place of the NTP whose offset and
jitter values are much lower?Right now in our current system the NTP board is
used simply for time synchronization and not for any other processes so it is
also not busy with handling a lot functions.

gpsd: Read 35 chars to buffer offset 0 (total 35):
2447505a44412c3139313430312e3030302c30352c30322c323030392c2c2a35360d0a
gpsd: Packet type 0 accepted 35 =
2447505a44412c3139313430312e3030302c30352c30322c323030392c2c2a35360d0a
gpsd: Packet discard of 35, chars remaining is 0 =
gpsd: <= GPS: $GPZDA,191401.000,05,02,2009,,*56
gpsd: carrier-detect on /dev/ttyM0 changed to 0
gpsd: carrier-detect on /dev/ttyM0 changed to 1
gpsd: ntpshm_pps: not in locking range: -9550131
gpsd: polling 4
gpsd: Read 35 chars to buffer offset 0 (total 35):
2447505a44412c3139313430322e3030302c30352c30322c323030392c2c2a35350d0a
gpsd: Packet type 0 accepted 35 =
2447505a44412c3139313430322e3030302c30352c30322c323030392c2c2a35350d0a
gpsd: Packet discard of 35, chars remaining is 0 =
gpsd: <= GPS: $GPZDA,191402.000,05,02,2009,,*55
gpsd: carrier-detect on /dev/ttyM0 changed to 0

Sincerely,
Runa Dahal



More information about the questions mailing list