@Homerih: in case you haven’t checked it already, all information about OpenSprinkler can be found at http://www.opensprinkler.com. It runs an ATmega328 microcontroller itself so you don’t need to attach it to any arduino. The microtronoller runs a full-featured program which serves the webpage, and carries out the water schedules. The webpage requires some Javascripts that are currently hosted on rayshobby.net server. Dan’s Raspi scripts are designed to offload these Javascripts to a Pi server, as well as to log the sprinkler status (which the controller doesn’t do itself). Also, using a Pi to interface with OpenSprinkler makes it easy to introduce weather-based features and anything that requires computation beyond what a simple microcontroller can do.