In my work role I’m regularly dealing with GNSS & atomic clock systems that deliver time, phase & frequency accurate to nanoseconds for those applications that require them e.g. Telecom (4G LTE-A & 5G), Power/Utility, Broadcast & Financial Services to name but a few.
But it’s not always about nanoseconds – here’s a selection of tiny clocks that are almost in sync to the nearest second 🙂
USB-RTC on the EncroPi synced by hand/eye to the laptop’s clock, M5Stick synced to (S)NTP over WiFi and the tty-clock display on a Raspberry Pi 400 synced to NTP using chrony. The NTP server used is a local stratum 1 instance (Raspberry Pi getting a 1PPS from a ublox NEO-M9 eval board).
The M5Stick features a built-in real-time clock (RTC) and also features a temperature/relative humidity sensor module but the temperature data is inaccurate as it suffers from self-heating; conducted via the connector pins from the main board 😦
The micropython used on the EncroPi stick takes about 4s from hitting “run” in Thonny before it actually sets the on-board RTC, lots of trial-and-error before getting it set close (by eye) to the other clocks’ displayed time.
Series 3 256k – Series 3a 2M – HC120 – even sync’d by GPS!
Room 7609 
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