The FlexRay serial data protocol is being considered in automotive vehicle architectures as an enabler for active safety, time critical systems due to the advantages it provides for time-determinism, increased data bandwidth, and multiple data channels to support fault tolerance strategies. To improve the robustness/availability of the electrical/physical layer when used for these critical applications, a FlexRay Active Star device is available. The Active Star is part of the physical layer and facilitates the creation of robust, fault tolerant network systems by partitioning the network into individual branches connected to one or more ECUs. This partitioning allows fault confinements and isolation activities to be performed at individual branches with minimal disruption to network communication.
This paper describes the investigation of Active Star capabilities and some complexities related to their network integration. Included are descriptions of specific topologies, clique formation of individual sub-networks, and use of dual channels. A case study illustrates the integration of Active Stars in a dual channel FlexRay network, the detailed interface to a host ECU via SPI communication, and topologies with additional Active Stars. Additionally, the paper will illustrate some Simulink models and S-functions, as well as describe some fault injection mechanisms utilized to verify the Active Star behavioral characteristics. The discussion is substantiated with details from an actual bench implementation.