“Time and event triggered communication scheduling for automotive applications”

Abstract

The CAN protocol has become the primary choice of protocol for real time communication sub systems within automotive electronics applications by a number of European car and heavy truck manufacturers. This is despite the fact that CAN, according to many opinions, is unsuitable for distributed real-time applications with hard real-time requirements due to the protocol’s bus contention. This mechanism is likely to introduce jitter, which sometimes is highly undesirable regardless of application criticality. The latest protocol specification TTCAN (Time Triggered CAN), addresses exactly this problem. With the TTCAN extension the CAN protocol has matured. It now support time-triggered operation as well as priority based event triggered message handling. In this paper, we will present a method for message scheduling and analysis in real time systems using TTCAN/CAN hybrid communication systems. We have applied our model and used our scheduling method on a non-trivial set of messages designed to be representative for a real application. The message set consists of 65 different messages, divided into three classes based on their respective timing requirements.

We describe our method as well as our results. Our primary objective with this paper is to provide the reader with new ideas and concepts addressing application-derived problems in real-time communication scheduling. We concentrate on heuristic methods to solve engineering problems rather than formal methods to solve general scheduling problems.

Keywords:

Hard real-time requirements, automotive electronics applications, heuristic scheduling