Pi Zero cluster lights - cjus/hydra-cluster GitHub Wiki

The Pi Zeros sitting on the ClusterHat utilize an LED strip to indicate their status.

The monitor Pi 3 sends Pi Zero status information to the 4th Pi Zero which in turn displays the status on its connected LED strip.

Because the LED strip is controlled via Python, a Python based Flash service is used to accept requests to display status.

http://mattrichardson.com/Raspberry-Pi-Flask/