A practical implementation of the fault-tolerant Daisy-chain clock synchronization algorithm on CAN

Networked processing units are becoming widely used in the automotive embedded system domain aiming not only to reduce vehicle weight and cost but also to assist the driver to cope with critical situations. Because the fact that these embedded networked systems are strictly involved with human safety, there is a high demand on dependability requirements which can only be guaranteed if active redundancy is employed. Considering that the processing units are usually connected by a shared serial media, the underlying communication platform is the most important building block. It must provide low-level support for deterministic data transmission as well as a global time base to coordinate the actions of replicated units. Within this context, this paper presents the development of the fault-tolerant Daisy-chain clock synchronization algorithm over the CAN protocol, resulting in an highly optimized communication architecture for safety-critical applications. Implementation issues and some obtained practical results are also discussed in the paper