Orange Pi Zero NTP Stratum 1 PPS GPS Server with Armbian OS. Link to the Tutorial - http://schwartzel.eu3.org/ntp-stratum1.html This tutorial uses a 3.3V capable GPS module with PPS output - TOPGNSS GN-701 (u-blox 7) but other similar modules should work.   This tutorial is for the Orange Pi Zero, but will probably work for other boards.   I couldn't easily do a comprehensive hardware and software tutorial on this forum, so I've published it on my web server and linked