A CoAP-gateway for smart homes

The ”Internet of Things” has led to a number of standardization efforts that can make proprietary protocols for home automation obsolete. One of the latest developments is the Constrained Application Protocol (CoAP) that is intended to be used as the HTTP-replacement for smart objects that are connected to the Internet. Early adaptors in industry and academia already have developed a plethora of applications that build on this new standard and have contributed valuable insights and implementation experience. While most of the new applications interoperate in a reasonable manner, the integration of legacy is one of the biggest challenges. Many existing protocols for home automation have been designed with a narrow focus on very limited devices that communicate with each other in a local network. CoAP, in contrast, mimics the architectural style that represents the fundamental basis of the Web, and therefore follows a very different design approach. In this paper, we present a basic design concept to interconnect CoAP and the proprietary FS20 protocol for home automation. The key aspects of our approach are the mapping of FS20 device addresses to path segments of CoAP URIs and to map FS20 commands to the four basic CoAP operations for creation, retrieval, update and deletion of resources, and the dynamic discovery of new nodes to register their capabilities with the CoAP service. To prove the feasibility of this approach, we have developed a multi-protocol gateway for a popular low-budget integrated access device.