An Experiment in Design and Analysis of Real-Time Applications

2006

The object-oriented paradigm has become popular over the last years due to its characteristics that help managing the complexity in computer systems design. This feature also attracted the embedded systems community, as today's embedded systems need to cope with several complex functionalities as well as timing, power, and area restrictions. Such scenario has promoted the use of the Java language and its real-time extension (RTSJ) for embedded real-time systems design. Nevertheless, the RTSJ was not primarily designed to be used within the embedded domain. This paper presents an approach to optimize the use of the RTSJ for the development of embedded real-time systems. Firstly, it describes how to design real-time embedded applications using an API based on RTSJ. Secondly, it shows how the generated code is optimized to cope with the tight resources available, without interfering in the mandatory timing predictability of the generated system. Finally it discusses an approach to synthesize the applications on top of affordable FPGAs. The approach used to synthesize the embedded real-time system ensures a bounded timing behavior of the object-oriented aspects of the application, like the polymorphism mechanism and read/write access to object's data fields.

1994

This thesis describes the calculation of execution times in the object-oriented language RealTimeTalk (RTT). RTT is an object-oriented language for hard real-time systems. Hard real-time systems are systems where all tasks must fulfil the specified time requirements. State of the art of execution time calculation in real-time systems is presented, and the different approaches are discussed and compared to the RTT approach. RealTimeTalk (RTT) is presented. The algorithms and data structures of an implementation of execution time calculation in RTT are described. Results and some limitations in the method are discussed. Preface. This licentiate thesis is a part of a joint research project between CUS (Department of Real-time Computer Systems) at the University of Mälardalen in Västerås and the Department of Machine Elements at KTH in Stockholm. Supervisors have been Prof. Sören Andersson and Dr. Jan Wikander at the Damek research group (Computer Controlled Machinery). The work has been supported by a reference group, consisting of Prof. Bud Lawson, Tech. lic. Ulf Backman and representatives of Swedish companies (ABB Automation, DeLaRue Inter Innovation and CelsiusTech). The project RTT started in 1990 as an idea to show that, opposite to many peoples opinion, real-time systems could be constructed with object-oriented techniques. A number of presentations and papers have communicated the progress of the project. The first presentation was given in Uppsala at the SNART (Swedish Work Group for Real-Time) conference 19-20 august 1991. A paper was presented at the IFAC/IFIP international workshop on real-time programming (WRTP'92) in June 1992 [Brorsson92]. Another paper was presented at the Fifth Euromicro Workshop on Real-Time Systems, Oulu, Finland, June 1993 [Eriksson93]. A recent presentation was given at the SNART conference in Stockholm in august 1993. Parallel to this thesis, another thesis [Eriksson94]has been written by my colleague Christer Eriksson at CUS. His thesis describes the RTT framework and run-time system in more detail and makes a comparison to the state of the art. My work in the RTT project has been supported by NUTEK and by internal research funding at the University of Mälardalen. I would like to thank my supervisors and the members of the reference group. Thanks also to all my colleagues at CUS and at Damek for friendly cooperation. Special thanks to Christer Eriksson for all the creative discussions, and to Harriet Ekwall for the friendly atmosphere at CUS.

Proceedings of the IEEE, 2003

We present a methodology for building timed models of real-time systems by adding time constraints to their application software. The applied constraints take into account execution times of atomic statements, the behavior of the system's external environment, and scheduling policies. The timed models of the application obtained in this manner can be analyzed by using time analysis techniques to check relevant real-time properties. We show an instance of the methodology developed in the TAXYS project for the modeling and analysis of real-time systems programmed in the Esterel language. This language has been extended to describe, by using pragmas, time constraints characterizing the execution platform and the external environment. An analyzable timed model of the real-time system is produced by composing instrumented C-code generated by the compiler. The latter has been re-engineered in order to take into account the pragmas. Finally, we report on applications of TAXYS to several nontrivial examples.

Lecture Notes in Computer Science, 2004

In this work, we propose a complete methodology called RESS (Real-Time Embedded Software Synthesis) for the automatic design of real-time embedded software. Several issues are solved, including software synthesis, software verification, code generation, graphic user interface, and system emulation. To avoid design errors, a formal approach is adopted because glitches in real-time embedded software are intolerable and very expensive or even impossible to fix. Time Complex-choice Petri Nets are used to model realtime embedded software, which are then synthesized using a time extended quasi static scheduling algorithm. The final generated C code is prototyped on an emulation platform, which consists of an 89C51 microcontroller for executing the software, an FPGA chip for programming the hardware for different applications, and some input/output devices. Two application examples are used to illustrate the feasibility of the RESS methodology.

1993

In contrast to most of the other studies which only consider selected topic(s) and typically deal with issues of higher levels of design, the research project outlined in this paper is using a holistic approach to real-time application design issues, It is set up in layers starting with a predictably behaving computer hardware architecture, followed b y an appropriate programming language and, finally, a tool for automated application development. Each of these layers is providing a sound basis for the next higher one.

2005

The growing complexity of today's embedded real-time systems demands new methods and tools in order to manage the problems of design, analysis, integration and validation of complex systems. This paper describes an object-oriented platformbased design process for real-time embedded systems. The proposed approach promotes a smooth transition from high-level UML specification to implementation, which is composed by hardware and software components. The transition from higher to lower abstraction levels is facilitated by the use of an OO realtime API, whose underlying facilities can be optimized according to the application needs and selected platform. An integrated toolset is used to support the intermediate steps of the design process. In order to illustrate the proposed approach and related toolset the design of an embedded real-time automation system for an "intelligent" wheelchair is presented.

2004

Petri net variants are widely used as a real time systems modeling technique. Recently, UML activity diagrams have been used for the same purpose, even though the syntax and semantics of activity diagrams has not been yet fully worked out. Nevertheless, activity diagrams seem very similar to Petri net semantics. UML, being the industry standard as a common object oriented modeling language needs a well-defined semantic base for its notation. Formalization of the graphical notation enables automated processing and analysis tasks. Petri nets can provide a formal semantic framework for the UML notations plus the behavioral modeling/analysis strength needed to system designers. This paper describes the methodology for creating the model of the RT application that would allow testing the correctness of the algorithm and the fulfillment of the time constraints at the design stage using UML and Petri Nets.

Distributed and Parallel Embedded Systems, 1999

Today's embedded systems (ES) are characterized by more and more parallelism, distribution over different locations and hard real-time (RT) requirements. Consequently, the modern, structured design process has to deal with heterogeneous requirements and restrictions. Especially the integration of HW-design tasks with SWdesign tasks and operating system functionality with respect to RT requirements is a main challenge. The integration leads to systems with enormous overall complexity because the complexity of each design partition itself has been doubled nearly every Today's embedded systems (ES) are characterized by more and more parallelism, distribution over different locations and hard real-time (RT) requirements. Consequently, the modern, structured design process has to deal with heterogeneous requirements and restrictions. The integration of several core competencies is essential for establishing a methodological structured design process for parallel distributed embedded realtime systems. In this paper we present an overall structuring of the design process as well as the Paradise Design Environment reflecting the design process structure. Our activities are based on wide, theoretically well-founded concepts and tool support is built upon these theoretically foundations.

1990

An environment for rapid prototyping and analysis of real-time systems is presented. The real-time system is specified using the language QUISAP and, from this specification, a model based on timed Petri nets for formal analysis and a prototype written in Ada for behavior analysis are built. Inappropriate handling of temporal constraints violations during prototype execution due to the Ada language can be improved with a new scheduling of tasks. Other improvements relate to the model of application objects, its ...

2008

This paper summarizes some techniques used in a project that goals to analyze Real-Time Systems features in a way that allows to model and to implement software and hardware components that will compose a framework repository to the automatic generation of Systems-on-a-Chip. Tools associated to that framework will allow co-design and software/hardware partitioning of such real-time features. The contribution of such project is to produce an adaptable multiplatform computational system that fulfills the real-time requirements of a particular application.