Using a planning scheduler in the CAN network

Abstract

Controller Area Network is a broadcast bus based on dynamic scheduling. Although timing performance can be evaluated if the message set is previously known, it becomes difficult to keep guarantees if on-line changes are to be made. This results in a lack of flexibility when real-time behaviour is of concern. In this paper the authors propose the use of a centralised planning scheduler on a CAN system to achieve operational flexibility while keeping guaranteed timing behaviour. The low run-time overhead of this scheduler makes if particularly suited when low-processing power microcontrollers are to be used. It is shown that the communication protocol derived is capable of handling centrally controlled periodic traffic without a significant penalty in bus load and can process changes in the system configuration or message parameters with a response time adequate for most applications.