Implementing real-time event channels on CAN-bus

Factory automation systems connect large numbers of autonomous, cooperating devices by fieldbus networks. Fieldbuses, however, provide rather low-level communication objects and their features regarding quality aspects of communication are difficult to assess and use for applications. We present an implementation of realtime event channels on the RTLinux that uses the CAN-bus as the communication media. The real-time event channel interfaces allow applications to specify quality aspects of the communication at a high level of abstraction. The paper presents a description of the middleware architecture used in the implementation. Special attention is given to implementation issues of real-time event channels as clock synchronization and the impact of controller hardware. Finally, we provide experimental results for event channels with different QoS properties.