My hands-on approach to dissecting IoT from the inside led me to fulfill a long-time dream of having an on-site Stratum-1 Network Time Protocol (NTP) server. NTP is the decades-old synchronization protocol that keeps networked computer clocks accurate.

The best-case scenario for an NTP server is being fed from a Stratum-1 time source, that is, for instance, connected to the source of a VERY accurate time, usually an atomic clock (also called, Stratum-0).

A good amount of Stratum-0 time sources is constantly floating over our heads! The GPS satellites, each one carrying at least two cesium atomic clocks (accurate up to 1 second every 300 million years).

The idea of using GPS as a time source is not new, there are dozens of commercial products available doing precisely that. But my goal is to make it cheap, accurate, self-contained, dual-powered (mains and batteries), wireless-enabled, and portable to use on the field in my HAM Radio activities. Powered by the ever-expanding universe of microcontroller units, this goal is closer than ever.

Current functionalities:

• Internal RTC synched from GPS satellites constellation (backed by CR2032 battery)


• Dual voltage powered


• Backup battery for the whole unit (18650)


• NTP and RDATE (RFC868) protocols supported


• WiFi functionality as a client or access point


• Syslog logging


• Configuration webpage for WiFi and Syslog, saving to persistent storage (LittleFS)


• Informative display with a timestamp, satellites in view, accuracy, wifi server, IP address


• Dual function button, short press switch information on display, long press disables WiFi


• Status at a glance, with dedicated 5mm LEDs for GPS lock, PPS signal, and WiFi status, as well as visible internal LEDs for charging and GPS module statuses