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What are all things the raspberry do here? I'm planning doing something like this and maybe use https://dl.dropboxusercontent.com/u/993383/Cosa/doc/html/index.html Cosa libraries with arduinos. The thing is do I need raspberry? If I'm able to install OpenHAB or dometicz on QNAP (NAS), maybe rasp is not needed? Then Id only need arduino gateway that is connected to the QNAP and some "slave" arduinos. QNAP doesn't have any sensors in it but USB devices can be connected to it.