Using GPS with PPS to synchronize clocks over the network

[@ahnhelnyc]

Followed this tutorial to use as a Stratum 1 PPS Time Server for OPNsense. Worked flawlessly with your precise guidance, thank you.

[@linuxtechschool4841]

Hi, Thanks a lot for your feedback. Regards.

[@goodtoshi]

Thank you very much for the tutorial. But if I understand correctly the output on 14:11, this server still uses NTP to set the "rough" time and then uses PPS to make it more precise. I think it would be even better to use GPS time (NMEA) as the source of the "rough" time which will make it completely autonomous and independent from the internet.

[@AhoyCapnLinux]

This is typically how it works. A 2D or 3D GPS lock allows for delta triangulation between multiple satellites, providing the "rough" time. From there, PPS driven by a super-accurate clock will further refine the time. In a Linux setup, typically something like GPSd will feed the GPS + PPS data to an NTP daemon such as chrony.

[@elements88xyz]

Highly appreciate you for this tutorial Rodrigo!

[@PramodKumar-es2ov]

Hi, You are connecting ping 1 of Raspberry Pi for GPS 8M Module. but in video you told us to connect pin no 2. Can you please clarify.

[@rbellido1]

Excellent video!

[@gooallen]

Thank you very much! I followed your tutorial and worked! If finially I need is "LTC timecode output for other device", will you have plan for PART II?

[@tusharsonawane4031]

The time delay was more than 500 nanoseconds. Right ?

[@nachovillazon4158]

Hello, first of all, congratulations on this tutorial, I find it very interesting. I'm trying to follow these steps on a Rasaberry Pi 5 with a Geekstory GT-U7 GPS module but when I get to the part where you have to restart "chrony" it returns the following error: Job for chrony.service failed because the control process exited with error code. Could you tell me why this could happen? I'm a newbie at this Thank you

[@AhoyCapnLinux]

That log is from journald and doesn't tell exactly what happens. Get the exact chrony error by running `journalctl -xe -t chronyd`, this will make debugging easier. Most likely, there is an error in your configuration file.

[@FlaxTheSeedOne]

Would love to see this shown not jsut with an NTP server but also PTP as the pi also supports that with the brodcom nic it has.

[@abyagowi7]

The precision you get from pulling from a regular GPIO will not be enough for PTP. You can give it a try and look for the precision over ethernet to another NIC with PPS output. If you build two setups you will see that the PPS output from the two NICs will have a jitter in the range of 100s microseconds. If 100s of microseconds is good enough for you then sure, you can use this method.

[@FlaxTheSeedOne]

@@abyagowi7 Thats what you use the PPS input on the pi for as it also has that.

[@AhoyCapnLinux]

The Pi he is using is the 3b. This Pi does *NOT* support hardware timestamping via the broadcom PHY* (the onboard chip. Not NIC, that is the port). The Pi 5 and the CM4 have support for PTP hardware timestamping.

[@AhoyCapnLinux]

This can be improved upon using the hardware timestamping functionality of a Raspberry Pi CM4 or model 5's ethernet PHY to send PTP throughout your network. Great video!

[@AdullKKU]

Thanks Sir