I'm considering such option. I found also that MODBUS is the protocol which can be used in order to communicate with PLC. I have found that there is a driver for linux for modbus. I'm now considering few hause automation solutions and wanted to find something usefull, scalable and good value for money. KNX is quite expensive, so I was looking for any some alternative solution, which is able to work with MCE and scalable and flexible in terms of programming so called scenes.