Developing a Novel Shared-Clock Scheduling Protocol for Highly-Predictable Distributed Real-Time Embedded Systems

The Controller Area Network (CAN) protocol is widely used in the development of distributed real-time embedded systems. It has previously been shown that a “Shared-Clock” (S-C) scheduling algorithm can be used along with CAN protocol to implement time-triggered network architectures. Previous work in this area has led to the development of four S-C scheduling protocols called TTC-SCC1, TTC-SCC2, TTC-SCC3 and TTC-SCC4 schedulers. This paper first reviews the four schedulers. Second, the paper provides a more general model for the TTC-SCC2 scheduler. Third, the limitations of the various S-C schedulers are discussed and an alternative S-C scheduling protocol is developed; which is referred to as TTC-SCC5 scheduler. The five schedulers are then evaluated and compared against a number of criteria including jitter behavior and resource requirements for practical implementation on low-cost embedded microcontrollers. The results presented in the paper show that the TTC-SCC5 scheduler is advantageous over the others since it integrates their key features while maintaining low implementation costs.