With this project you are able to connect a ArduinoNano to a RS485 Bus (operated by SoftwareSerial) and use it as a SensorShield. The parts are commercially available and cost about 5 €. There is also the possibility to add some resistors to attach some reed switches as well as a 1 inch raster connector to add an additional protoboard to test new applications (connected to 5V, GND, 2 analog and 4 digital pins). Originally this project is built to fit in a power line switch case (circle diameter of 60 mm and 20 mm height) to be used as a part of a RS485 bus driven home automation system. Have fun!

see above.