My father-in-law has a small collection of "School Clocks", aka slave clocks. These are wall clocks that are synchronized with a central clock by a clever self-correcting pulse protocol. A few years ago we replaced his antique master clock with an arduino to drive his slaves. We added an ethernet board so the electronic master could get the time itself from NIST. A project article was published in Nuts & Volts:
http://www.nutsvolts.com/magazine/article/january2015_Fox The source code for the clock is here:
https://github.com/phord/master_clockThis year we ported the clock driver to the
Digistump Oak. It was fairly easy to port once I got around the initial Oak and Particle issues. The code is on a separate branch for now:
https://github.com/phord/master_clock/tree/digistump-oakDad's still working on the level-shifters to drive his clock from the Oak, but the code seems to be working fine on its own.
In the end we will have replaced the wired-ethernet arduino setup ($75) with the wireless Oak ($11), got a much smaller footprint, and put the slaves on the cloud at Particle.io.
More on master clocks:
