Re: Help needed to configure and compile gpsd to run on a Raspberry Pi 4 and NOT use systemd

[Michael Simpson]

Hi Mick

here is the relevant bits from my servers -probably mangled by email

     remote                                   refid      st t when poll reach   
delay   offset   jitter
=======================================================================================================
*SHM(1)                                  .PPS.            0 l    -   16  377   
0.0000   0.0120   0.0006
-SHM(0)                                  .GPS.            0 l    5   16  377   
0.0000  12.4478   0.4680



*SHM(1)                                  .PPS.            0 l   12   16  377   
0.0000   0.0275   0.0042
-SHM(0)                                  .GPS.            0 l   15   16  377   
0.0000  16.6947   0.6384

unfortunately I am still using systemd leading to issues with gaps using 
sockets 
-systemd preemptively grabs hold of the socket and I haven’’t worked out the 
correct incantation to stop it.


BTW the ntpleapfetch from ntpsec needs altered post install as the 
leap-seconds.list is no longer valid

opening the file in /usr/local/bin with your favourite editor and changing the 
LEAPSRC to LEAPSRC="https://data.iana.org/time-zones/data/leap-seconds.list” 
makes it work

/mike

> On 20 Nov 2024, at 19:41, Mick Durkin <mickdurkinuk@gmail.com> wrote:
> 
> Hi Gary & Mike,
> 
> We implemented Mike's suggestion about adding the "nohz=off" parameter
> to the end of the single line in "cmdline.txt"and rebooted the Pi.
> 
> Having reviewed the "gpsd -nN -D 4 /dev/ttyAMA0" log from yesterday,
> it looked like pps0 was sending data to SHM(1), so we issued "gpsd -n
> /dev/ttyAMA0" and "ntpd -gN" commands (ntpd was a fresh install from
> NTPsec's git) and the output from "ntpq -p" looks good(ish).
> 
> Here is a single shot view:-
> 
> [root@pihole:~]$ ntpq -p
> 
>     remote                                   refid      st t when
> poll reach   delay   offset   jitter
> =======================================================================================================
> *SHM(1)                                  .PPS.            0 l    1
> 2  377   0.0000  -1.6773   0.0696
> +ntp2.wup-de.hosts.301-moved.de          205.46.178.169   2 u    3
> 16  377  25.5152   1.5299   0.7698
> -hc.gommels-bienen.de                    205.46.178.169   2 u    2
> 16  377  27.4352  -0.1648   2.7005
> -server1a.meinberg.de                    131.188.3.222    2 u    1
> 16  377  28.1533   0.2503   0.9983
> +time.cloudflare.com                     10.67.8.182      3 u    -
> 16  377  11.6901   1.1580   0.4343
> -SHM(0)                                  .GPS.            3 l    7
> 8  377   0.0000 -130.338   3.2722
> LOCAL(0)                                .LOCL.           5 l    -
> 64    0   0.0000   0.0000   0.0000
> [root@pihole:~]$
> 
> This was after a few minutes run, so maybe the offset and jitter
> values for PPS will settle down. At least, ntpd is locking on to the
> PPS signal and has a couple of externals with a '+' as well.
> 
> Maybe we can say that we have a good installation now?
> 
> As to Gary's query reference Pi3 and the "dtoverlay=disable-bt"
> addition to /boot/firmware/config.txt, that was not any fault of the
> gpsd documentation. That came straight from the original YouTube
> tutorial follwed back before I got involved with trying to "use gpsd
> without systemd and NTPsec instead of chrony". Again, that video might
> have been recorded back pre-Pi4. Could it be tied in with changes
> brought in with the Pi3 vs earlier devices or new-at-the-time distros?
> Certainly, it is still relevant to the Pi4.
> 
> If it is considered that our setup is "valid", maybe some of the
> pitfalls could be added to the gpsd site documents? We can easily
> summarise what we did, both initially (h/w setup) and relevant changes
> to the "config.txt" and "cmdline.txt" if it would help.
> 
> Can anyone (I reckon Mike is a likely candidate) running a similarly
> configured Pi 4 (gpsd not under systemd with an NTPsec derived ntpd)
> let us know what kind of offset and jitter  numbers they get from PPS?
> 
> BR
> 
> Mick
>