Integrating Subscription-based and Connection-oriented Communications into the Embedded CORBA for the CAN Bus

Abstract

Recently emerging component-based middleware technologies such as CORBA are widely believed to be a viable solution to the software complexity problem of a distributed embedded computer control system. However, general purpose middleware systems are not immediately applicable to a distributed embedded system since they should run in a platform with severe resource limitations. In this paper, we present the design of CAN-CORBA, an environment-specific CORBA for CAN-based distributed control systems. The ORB core of the CAN-CORBA has the following properties. (1) It supports subscription-based group communication as well as the classical connection-oriented point-to-point communication of CORBA; as a result, it better services the data multicasting requirement of typical control systems. (2) It significantly lowers the amount of message traffic required for each CORBA method invocation so that even the slow broadcast bus of the CAN can tolerate the overhead of CORBA method invocations. To seamlessly integrate two communication schemes into our extremely light-weight ORB, we design a transport layer protocol on the CAN that can support up to four different upper level protocols.

We have implemented the CAN-CORBA on the mArx real-time operating system we have developed at Seoul National University. Our experiments clearly demonstrate that it is feasible to use CORBA in developing distributed embedded control systems possessing severe resource limitations.