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Reliable Real-Time Communication in CAN Networks
Ref: HURRAY-TR-0301       Publication Date: Dec 2003

Abstract:
Controller Area Network (CAN) is a fieldbus network suitable for small-scale Distributed Computer Controlled Systems (DCCS), being appropriate for sending and receiving short real-time messages at speeds up to 1Mbit/sec. Several studies are available on how to guarantee the real-time requirements of CAN messages, providing pre-run-time schedulability conditions to guarantee the real-time communication requirements of DCCS traffic. Usually, it is considered that CAN guarantees atomic multicast properties by means of its extensive error detection/signalling mechanisms. However, there are some error situations where messages can be delivered in duplicate or delivered only by a subset of the receivers, leading to inconsistencies in the supported applications. In order to prevent such inconsistencies, a middleware for reliable communication in CAN is proposed, taking advantage of CAN synchronous properties to minimise the run-time overhead. Such middleware comprises a set of atomic multicast and consolidation protocols, upon which the reliable communication properties are guaranteed. The related timing analysis demonstrates that, in spite of the extra stack of protocols, the real-time properties of CAN are preserved, since the predictability of message transfer is guaranteed.

Luis Miguel Pinho

,

Francisco Vasques

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