See last page for copyright and document info, File: Reeve_GpsNtp-Pi_Setup.doc, Page 29
Scroll down to the line starting with
fudge 127.127.28.0
and adjust the time1 parameter. When finished type
CTRL-X (Exit), Y (yes), Enter to save and close the editor. Now, restart the NTP service:
sudo service ntp restart
If you decide to recalculate the average offset using the above procedures, wait at least another day or two.
Avoid unnecessarily changing the time1 value. In my lab systems the time1 value in the Adafruit GPSD driver is
+0.534 s and in the HAB Supplies GPSD is +0.125 s.
The overall NTP server system can be tested by installing an NTP client program on a PC on the same LAN.
Example clients are SymmTime (not compatible with Windows 7x64 or later), Dimension4 and Meinberg NTP
(Note: Do not confuse the Meinberg NTP Monitor software tool with the NTP software; both are available on
Meinberg’s website). Download locations for these and similar programs may be found by ordinary internet
search. The preferred client, by far, is NTP itself. The Windows version may be obtained at {
NTP-Win
}.
After installation, setup the NTP client to use the IP address of the RPi NTP server. For example, the SymmTime
setup is shown below for a GpsNtp-Pi lab system with IP address 10.0.0.32. In this case, I clicked Add Server in
the Sync Servers window (left), specified the lab system IP address and then removed all other servers from the
upper frame with the down-arrow between the frames. The Synchronization Status window (right) shows the
status of the new server. Note that the reference clock is KPPS and stratum level is 1, indicating proper
operation of the RPi NTP server.
This completes final adjustments and checks of the RPi as a standalone NTP server.
Tweak: The PPS jitter in some systems is reduced by a small tweak to the cmdline.txt file in the /boot/ directory.
At the command line prompt enter
sudo nano /boot/cmdline.txt
At the end of the single line in this file, add
nohz=off
with one space between the new text and existing text.
When finished type CTRL-X (Exit), Y (yes), Enter to save and close the editor. Now, reboot the NTP server:
sudo reboot
