Building a Stratum 1 NTP Server Using Raspberry Pi

[stephenw10]

Are those values actually in milliseconds or is it microseconds and just mislabeled?

Steve

[kiokoman]

@stephenw10
the values from ntpq afaik is milliseconds ?

[stephenw10]

Yes, it reads in milliseconds but that can get confusing when is shows a value like 0.001 (1μs).

Values in microseconds are what you should expect if PPS is working.

Less than 1μs is impressive. I generally see between 1-2μs here.

Steve

[q54e3w]

@kiokoman said in Building a Stratum 1 NTP Server Using Raspberry Pi:

and it drift up and down very mutch during the day compare to the adafruit

Is your device thermally stable, without some kind of TCXO its likely drift. I see fluctuations around 11am to 4pm as the sun hits the room where my timing hardware is located. Temperature corrected devices are unaffected.

Also, different drivers are very likely to introduce different levels of performance so try and ensure you are using same drivers (type 22 PPS vs SHM type 28 etc).

[kiokoman]

yeah, i'm using only type 20 and type 22
but i think i was finally able to find a configuration that suits it

http://www.philrandal.co.uk/blog/archives/04-01-2019_04-30-2019.html
with some minor adjustment

[kiokoman]

@tman222

I'll answer your question about nohz
it does not work on raspberry pi 4 + raspbian
the kernel isn't configured to allows the nohz parameter to work
also, I found that you can only use
flag 3 0 (use the ntpd clock discipline)
and not
flag 3 1 (use the kernel discipline)
for PPS
if you try to use flag 3 1 you see in the syslog this:

refclock_params: time_pps_kcbind: Operation not supported

this is because the kernel is compiled without CONFIG_NTP_PPS

obviusly
as a good nerd I recompiled ...

this is ublox now

server 127.127.20.0 mode 89 iburst prefer minpoll 2 maxpoll 4
fudge 127.127.20.0 flag1 1 flag3 1 time1 0.0 time2 0.025 refid GPS

pi@raspberrypi3:~/linux $ uname -a
Linux raspberrypi3 4.19.118-v7lntp+ #1 SMP Fri Dec 11 14:42:08 CET 2020 armv7l GNU/Linux

pi@raspberrypi3:~/linux $ ntpq -crv -pn
status=041d leap_none, sync_uhf_radio, 1 event, kern,
version="ntpd ntpsec-1.1.3 2019-11-18T06:04:00Z", processor="armv7l", system=" Linux/4.19.118-v7lntp+", leap=00, stratum=1, precision=-20, rootdelay=0.0, rootdisp=2.18, refid=GPS, reftime=e37e600c.8bd6769d 2020-12-11T21:15:56.546Z,
clock=e37e6018.d0a57250 2020-12-11T21:16:08.815Z, peer=11020, tc=4, mintc=0, offset=7.8e-05, frequency=-18.907623, sys_jitter=0.000277, clk_jitter=0.000728, clk_wander=0.001816, tai=37, leapsec="2017-01-01T00:00Z",
expire="2021-06-28T00:00Z"
     remote                                   refid      st t when poll reach   delay   offset   jitter
=======================================================================================================
oNMEA(0)                                 .GPS.            0 l   12   16  377   0.0000   0.0001   0.0003

[sagliklihayatimiz]

This post is deleted!

[tman222]

Hi all -

Wanted to follow up on this thread as I recently acquired a Stratum 1 NTP server for my network (LeoNTP - very cool little device). Currently, I have it setup as the only NTP time server on pfSense (i.e. no other servers are configured). Is this an acceptable setup, or should I be adding a few additional public Stratum 1 servers as a sanity check, and set the LeoNTP device as the preferred server? I realize with just one server I don't have any redundancy, but is that the only main drawback? Thanks in advance!

[kiokoman]

@tman222
if I remember correctly you need at least 3 good ntp server on the list to see if the leontp is working correctly
without any reference you don't know if the time is correct

[q54e3w]

@tman222 I run a few Pi based GPS devices that don't offer the same accuracy, and a few external sources for backup. The LeoNTP takes precedence as primary source of time due to its accuracy.

[tman222]

Thanks @kiokoman and @q54e3w, I really appreciate the help and advice. Do either of you use the "prefer" keyword on your local NTP server(s), or do you leave the server choice solely to the selection algorithm? Thanks again.

[kiokoman]

@tman222
this is my config for the ublox

server 127.127.20.0 mode 89 iburst prefer minpoll 2 maxpoll 4
fudge 127.127.20.0 flag1 1 flag3 1 time1 0.0 time2 0.025 refid GPS

tos mindist 0.060

server 192.168.10.200
server 151.3.106.211
server ntp1.inrim.it
server ntp2.inrim.it
pool 0.it.pool.ntp.org
pool 1.it.pool.ntp.org

this is the results

remote                          refid      st t when poll reach   delay   offset   jitter
========================================================================================
oNMEA(0)                        .GPS.            0 l   11   16  377   0.0000   0.0002   0.0003
+192.168.10.200                 .GPS.            1 u   42   64  377   0.0996  -0.0002   0.0149
+151.3.106.211                  .GPS.            1 u   40   64  377  24.2144   0.1478   0.9674
-193.204.114.232                .CTD.            1 u   59   64  377  25.2698  -4.7052   0.3729
+193.204.114.233                .CTD.            1 u   49   64  377  12.5229   0.0942   0.3967
 0.it.pool.ntp.org              .POOL.          16 p    -  256    0   0.0000   0.0000   0.0010
 1.it.pool.ntp.org              .POOL.          16 p    -  256    0   0.0000   0.0000   0.0010
-37.247.53.178                  193.204.114.233  2 u   57   64  377  11.9465   1.0424   0.6543
-162.159.200.123                10.20.14.167     3 u   37   64  377  25.2151   0.8878   0.4707
+212.45.144.206                 193.204.114.232  2 u    9   64  377  10.5258   0.5104   0.3046