Help With PPS / GPSD In Proxmox (Linux)

[Ed Armstrong]

Hi, I'm having a little trouble getting the PPS to work well in proxmox. 
The device I am working with is a little fanless mini computer based on 
an Intel N100 processor. it is running Proxmox 8.1.4. According to their 
site, "Proxmox Virtual Environment is based on Debian GNU/Linux and uses 
a custom Linux Kernel." when I SSH in, it shows the message:


Using username "root".
Linux Proxmox 6.5.13-1-pve #1 SMP PREEMPT_DYNAMIC PMX 6.5.13-1 
(2024-02-05T13:50Z) x86_64

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Tue Mar 19 12:59:47 2024 from 192.168.0.5
root@Proxmox:~#


I am hoping to use this as my network NTP server, and also allow public 
access, it seems a nice upgrade from my raspberry pi 2. I do not 
necessarily need microsecond accuracy, and have no plans to implement 
PTP, just want a decent running server. I've got the signal converted to 
proper serial voltage levels, and have it attached to a serial header on 
the motherboard. Signal looks very clean on an oscilloscope.

If I run ppscheck, I get the following.

root@Proxmox:~# ppscheck /dev/ttyS0
# Seconds nanoSecs Signals
1710519439.933917435 TIOCM_CD
1710519440.001331406
1710519440.101356544 TIOCM_CD
1710519441.001316803

I have edited /etc/default/gpsd to include DEVICES="/dev/ttyS0" And then 
rebooted, but trying to run ppstest /dev/pps0 receives a bunch of 
timeouts. I have also tried pps1 with the same results. If I "systemctl 
stop gpsd.socket gpsd.service" And then try "gpsd -D 5 -N -n 
/dev/ttyS0", I get a bunch of data which includes

gpsd:ERROR: unable to connect to the DBUS system bus
gpsd:pROG: shmget(0x47505344, 24512, 0666) for SHM export succeeded
gpsd:pROG: shmat() for SHM export succeeded, segment 8
gpsd:INFO: stashing device /dev/ttyS0 at slot 0
gpsd:pROG: no /etc/gpsd/device-hook present, skipped running ACTIVATE hook
gpsd:INFO: SER: opening GPS data source type 2 at '/dev/ttyS0'
gpsd:INFO: SER: speed 9600, 8N1


I believe the "gpsd:ERROR: unable to connect to the DBUS system bus" Is 
because I have no desktop present, if I understand that correctly.
I am not sure what "gpsd:pROG: no /etc/gpsd/device-hook present, skipped 
running ACTIVATE hook" is all about, is this a problem?

and Further down in the output

gpsd:INFO: startup at 2024-03-15T16:29:12.000Z (1710520152)
gpsd:pROG: KPPS:/dev/ttyS0 assert 0.000000000, sequence: 0, clear 
1710520153.001330528, sequence: 1 - using: clear
gpsd:pROG: KPPS:/dev/ttyS0 Clear cycle: 1710520153001330, duration: 
1710520153001330 @ 1710520153.001330528
gpsd:pROG: PPS:/dev/ttyS0 Clear cycle: 1710520153001330, duration: 
1710520153001330 @ 1710520153.001330528
gpsd:pROG: KPPS:/dev/ttyS0 assert 1710520153.101386295, sequence: 1, 
clear 1710520153.001330528, sequence: 1 - using: assert
gpsd:pROG: KPPS:/dev/ttyS0 Assert cycle: 1710520153101386, duration: 
100055 @ 1710520153.101386295
gpsd:pROG: PPS:/dev/ttyS0 Assert cycle: 1710520153101386, duration: 
100055 @ 1710520153.101386295
gpsd:pROG: PPS:/dev/ttyS0 Assert ignored missing last_fixtime
gpsd:IO: UBX: len 60

This seems to indicate to me that the kernel PPS module is loaded and 
sees /dev/ttyS0. At some point during the output, I get a timeout error, 
after that all the outputs is a timeout error every few seconds. Not 
sure what to make of this.

Nothing I have tried gets me to see a signal at /dev/pps0, and I have 
had no luck getting any information into Chrony except by synchronizing 
to online servers or a raspberry pi NTP server I currently have running.

I would appreciate any help any of you can give with getting the time 
data and PPS into Chrony (or ntpd). I also wish to make GPSD accessible 
over the network, As I need to connect "Lady Heather" so it can get 
information about the GPSDO.

I am fairly sure that the problem is me, but I am not having any luck 
figuring it out myself. I tried posting on the proxmox forum but didn't 
get a response. Searching online is also not getting me any answers, or 
at least nothing I can recognize as an answer, again the problem may 
very well be me and my poor understanding of Linux.

Can anybody here suggest what I need to do to get this working? Or 
perhaps tell me there is a problem which will prevent it and I should 
just continue using the raspberry pi?


I appreciate whatever advice you can give.

Ed