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ROFES: Real-Time CORBA for embedded systems

The goal of the project

First generation real-time applications were running on single processor environments since the problems to be solved were relatively simple. Nowadays applications like avionics, telecommunication, process control and distributed interactive simulation need real-time properties in a distributed environment. Middlewares like CORBA and DCOM help to improve the flexibility, extensibility, maintainability and reuseability of distributed applications. But these middleware architectures can not be used to build an avionics mission control application because they do not support real-time features. Therefore the Object Management Group develops a specification for CORBA with a real-time extension and called this specification Real-Time CORBA.


Many real-time applications run on embedded systems. However, CORBA is too large to meet the exact size and performance requirements for such applications. This scenario requires a cut-down version of CORBA, which has been specified by the Object Management Group and is called minimumCORBA. We have implemented a prototype of Real-Time CORBA, with the aim to minimize the memory footprint. On operating systems with shared library support we implemented our ORB like a microkernel architecture. The ORB is seperated into serveral components, which can be dynamically loaded to the programm. Only the required components would be loaded into to memory. This promise a very low memory footprint. In particular our version of Real-Time CORBA is suitable for embedded systems. Therefore our project is called Real-Time CORBA for embedded Systems (ROFES). We will adhere to the OMG standards Real-Time CORBA and minimumCORBA. Besides Ethernet, ROFES supports other network architectures. By supporting these new network architectures we hope to achieve better real-time characteristics. One of these network architectures is the Scalable Coherent Interface (SCI) and the Controller Area Network (CAN).

A real-time operating system provides ideal support for real-time applications. However, the cost aspect and the acceptance of operating systems like Windows, Sun Solaris and Linux have generated a need for real-time functionality in these operating systems. For instance, Solaris is compatible with the real-time extension POSIX 1003.1b, although it is not possible to develop a hard real-time application in such an environment. Many companies and universities are developing real-time extensions for Windows and Linux. A very interesting real-time extension for Linux is Real-Time Linux. In Real-Time Linux, a small hard-realtime kernel and standard Linux share one or more processors in order to develop a system that can be used for applications like data acquisition, control and robotics while still serving as a standard Linux workstation. Therefore we implemented ROFES on Real-Time Linux, Linux, Windows XP/CE and LynxOS. We also develope a time-triggered ethernet protocol for Real-Time Linux and integrated this protocol into our Real-Time CORBA implementation. The first results of the time-triggered ethernet protocol integration and the SCI support promise a very good real-time characteristics of our Real-Time CORBA implementation.