Approaching the Limits of FlexRay

The aeronautic industry is strongly interested in utilizing the automotive FlexRay protocol. Economic benefits to be derived from the automotive mass market, and technological benefits arising from to the deterministic communication behavior are projected. The physical layer of the protocol is customized to suit automotive applications. The topology of aeronautic systems is more critical in terms of greater cable lengths and protection circuits. This paper therefore analyzes the suitability of topology implementations exceeding the recommendations defined in the FlexRay specification. This paper derives worst case signal integrity criteria for FlexRay and applies them to an exemplary aeronautic topology with six nodes and an overall length of 90 m. The paper highlights the fact that reliable communication is conditionally possible on the topology at data rates up to 5 Mbit/s.