Implementing the real-time publisher/subscriber model on the controller area network (CAN)

Designing distributed real-time systems as being composed of communicating objects offers many advantages with respect to modularity and extensibility of these systems. However, distributed real-time applications exhibit communication patterns that significantly differ from the traditional object invocation style. The publisher/subscriber model for inter-object communication matches well with these patterns. Any implementation of that model must address the problems of binding subscribers to publishers, of routing and filtering of messages, as well as reliability, efficiency and latency of message delivery. In the context of real-time applications, all these issues must be subject to a rigid inspection with respect to meeting real-time requirements. We argue that for embedded control systems built around smart microcontroller-powered devices these requirements can only be met when exploiting the properties of the underlying network. The CAN-Bus (CAN: Controller Area Network) which is an emerging standard in the field of real-time embedded systems is particularly suited to implement a publisher/subscriber model of communication. We present an implementation of the real-time publisher/subscriber model that exploits the underlying facilities of the CAN-Bus. In particular, we introduce a novel addressing scheme for publisher/subscriber communication that makes efficient use of the CAN-Bus addressing method. We provide a detailed design and implementation details along with some preliminary performance estimations.