I don't know where most of these parts came from, but when I opened my electronics junk drawer the other day I found an Orange Pi Zero+ and a serial GPS of dubious quality that also featured a PPS out. With these two parts in hand and a suitable project box, my weekend free time is suddenly consumed with a pending project: build a stratum 1 NTP server using only parts on hand.
OK, but what even is that word salad of a title?
Network Time Protocol (NTP) is a method of synchronizing clocks over the internet. Wikipedia has much better information than I could ever hope to provide here, but the gist is NTP servers are organized hierarchically based on their distance from known stable clock sources. This distance is referred to as the 'stratum' of the server. Stratum 0 is a master clock itself, such as a GPS, atomic clock, WWV signal, or other authoritative time source. Stratum 1 is any NTP server directly attached to a stratum 0 clock. Since my junk drawer project welds a microcomputer and GPS receiver together, it will (eventually) qualify as stratum 1 (with caveats).
Pulse Per Second (PPS) is a signal put out by time sources to define the precise beginning of a second. A GPS connected via serial port can vaguely define the time in its NMEA sentences, but PPS provides a stable 'tick-tock' to the time sentences.
