Non-preemptive scheduling of messages on controller area network for real-time control applications

Abstract

Scheduling messages on the controller area network (CAN) corresponds to assigning identifiers (IDs) to messages according to their priorities. If fixed priority scheduling such as deadline monotonic (DM) is used to calculate these priorities, then in general, it will result in low schedulability. Dynamic scheduling schemes such as earliest deadline (ED) can give greater schedulability, but they are not practical for CAN because if the ID is to reflect message deadlines then a long ID must be used. This increases the length of each message to the point that ED is no better than DM. Our solution to this problem is the mixed traffic scheduler (MTS), which is a cross between ED and DM, and provides high schedulability without needing long IDs. Through simulations, we compare the performance of MTS with that of DM and ED* (an imaginary scheduler which works like ED, except it needs only short IDs). We use a realistic workload in our simulations based on messages typically found in computer integrated manufacturing. Our simulations show that MTS performs much better than DM and at the same level as ED*, except under high loads and tight deadlines, when ED* is superior.