Enabling FlexRay for avionic data buses

Abstract

The aeronautic industry and its suppliers show increasing interest in utilizing the automotive FlexRay protocol for their applications, more than ever since an opening of the standard for all industries and field of applications becomes apparent. With its combination of deterministic and flexible c o m m u n ication and data rates up to 10 Mbit/s on a single twisted wire pair, FlexRay is a promising candidate for future system developments and the modernization of CAN based systems. Currently, the performance of the protocol is rather unknown i n a n aeronautic environment, in particular with respect to its physical layer. This paper analyzes the signal decoding process of FlexRay and derives dedicated signal integrity criteria for the protocol. An efficient method based on the transmission and evaluation of worst-case bit patterns is developed for the assessment of signal integrity on demanding topologies with significant attenuation and resulting inter-symbol interferences. RS485 is discussed as a possible alternative physical layer for the FlexRay protocol to improve the communication performance. Finally, a use-case topology with a harness length of 90 m is presented to evaluate the achievable performance when utilizing the FlexRay protocol. Signal integrity is demonstrated and validated on the topology at a data rate of 10 Mbit/s to prove the suitability of FlexRay for aeronautic applications.