I made a thing: GPS/PPS clock source for ntpd
Tip This is just a ‘pointer’ post.
All the details are in the kquinsland/yet-another-gps-pps-opnsense repo on github.
For the longest time, I had a dedicated raspberry pi with a GPS module acting as the ntp server for my home network. I chose to use a dedicated host for this because my router - at the time - did not have a serial port that I could leverage.
Recently, the miroSD card on the ntp pi died and I decided to leverage the serial port in my current router rather than re-build the operating system on the ntp host.