A Real-Time Java System on a Multithreaded Java Microcontroller

2005

The embedded real-time development community is investigating different approaches in order to provide modularity and reuse features for system design in this area, as well as a more appropriate mapping technique between requirements and implementation. The Java technology is very promising for this community, mainly after the research efforts on its real-time extension RTSJ-real-time specification for Java. However, there are still some critic factors related to the adoption of Java for real-time applications, and some of them deserve special attention. This paper reports a study of some of these decisive factors, such as the choice of the underlying operating system, the use of a middleware (virtual machine) or a native code, and the use of the Java real-time API (RTSJ)

2000

This paper describes experiences in using an O.O. language (Java) in designing, prototyping and evaluating a CPU manager. QoS Animator facilitates the execution of object oriented Java applications with time requirements and provides protection mechanisms to preserve system' s integrity against untrusted code. It is adapted to the system performance and provides a rate-monotonic based scheduling algorithm, WCET calculation at run-time and protection from high-CPU-consuming and "bad" code. The introduction of the Low Frequency Filter enhances the timeliness offered to applications in general-purposes Operating Systems (OS). The evaluation was done with a Windows NT specific prototype and proved successful.

2002

The Java language has several attractive features but cannot at present be used in on-board systems primarily because it lacks support for hard real-time operation. This shortcoming is in being addressed: some suppliers are already providing implementations of Java that are RTcompliant; Sun Microsystem has approved a formal specification for a real-time extension of the language; and an independent consortium is working on an alternative specification for real-time Java. It is therefore expected that, within a year or so, standardized commercial implementations of real-time Java will be on the market. Availability of real-time implementations now opens the way to its use on-board. Within this context, this paper has two objectives. Firstly, it discusses the suitability of Java for on-board applications. Secondly, it reports the results of an ESA study to port a software framework for on-board control systems to a commercial real-time version of Java.

2008 11th IEEE International Symposium on Object and Component-Oriented Real-Time Distributed Computing (ISORC), 2008

The partitioning of applications into hardware and software is an important issue in embedded systems, opening room for high level specifications as well as the exploration of different implementation strategies. This paper presents a software architecture to specify threads in hardware in the context of the Real Time Specification for Java (RTSJ) standard. There is a Java class that encapsulates hardware components, providing an abstraction layer to the application developer. Below this Java class, a wrapper hardware component provides a standard interface between RTSJ-based software components and the hardware that implements the thread behavior. This approach provides a high flexibility in choosing either a hardware or software implementation, allowing to postpone hardware/software partitioning to the very end of system development. The paper includes some quantitative data from an example containing hardware and software threads. While both implementations are compatible with the rest of the application from an interface pointof-view, they lead to very different timing and area results.

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.

1998

This dissertation proposes a new garbage-collected memory module architecture for hard real-time systems. The memory module is designed for compatibility with standard workstation architectures, and cooperates with standard cache consistency protocols. Processes read and write garbage-collected memory in the same manner as standard memory, with identical performance under most conditions. Occasional contention between user processes and the garbage collector results in delays to the user process of at most six memory cycles. Thus the proposed architecture guarantees real-time performance at fine granularity. This dissertation investigates the viability of the proposed architecture in two senses. First, it demonstrates that a fundamental component of the architecture, the object space manager, can be produced at a reasonable cost. Second, this dissertation reports the results of experiments that measure the performance of the proposed architecture under real workloads. Results of these experiments show that the architecture currently performs more slowly than traditional schemes; but this appears to be correctable by employing a more efficient function call mechanism that caches heap-allocated activation frames. Finally, this dissertation reports on some simple extensions to the C++ programming language to support slice objects. Slice objects, which are supported by the garbage collection architecture, are useful for implementing fragmentable arrays, i.e., arrays in which subarrays may be retained while unused elements become garbage and are collected. Experimental evidence demonstrates that slice objects can be used to implement strings more efficiently than at least some popular ii TABLE OF CONTENTS 1.

2000

Real-time programming is simply a necessity in many fields of application and specific real-time operating systems exist in order to fulfill the necessity of users to have time determinism in their applications. Anyway, often time constraints are not so hard and it is possible to identify hard and soft real-time applications, but time determinism keeps on being the mandatory requirement. The aim of this paper is that of describing the results of an activity devoted to investigate the possibility of real-time programming in a Java environment. A package has been developed in order to give a Java platform real-time capabilities of scheduling threads with time-based policies or by priority and events. A set of methods for threads to communicate through queues, messages, and mailboxes has been developed too.

2012

IEEE Transactions on …, 2010

Current trends in real-time systems identify Java as a new alternative to develop both centralized and distributed real-time systems. Many efforts have been devoted to develop the Real-Time Specification for Java (RTSJ), and there is substantial ongoing activity to produce a straightforward and valuable Distributed Real Time Specification for Java (DRTSJ). The current paper provides a contribution to this latter activity defining, from different angles, a synchronous scheduling service aligned with principles of some popular real-time architectures. This service orchestrates the system in such a way that it provides end-toend guarantees in the distributed transactions, guaranteeing their timely execution across the network and nodes. The service is described from two points of view: the system one, characterizing a portable model; and the programmer one, defining a distributed object-oriented implementation of a model based on Real-Time Remote Method Invocation (RTRMI). Finally, it also presents results of an implementation carried out to judge the efficiency of the service, offering a preliminary predictability and performance assessment of a distributed real-time Java technology.

Embedded Systems - Theory and Design Methodology, 2012

Real-Time Operating Systems and Programming Languages for Embedded Systems hardware architecture, as it is the case of RTSJ. This is undoubtedly a new scenario in the development of embedded real time systems. There is a wide range of hardware possibilities in the market (microcontrollers, microprocessors and DSPs); also there are many different programming languages, like C, C++, C#, Java, Ada; and there are more than forty real-time operating systems (RTOS) like RT-Linux, Windows Embedded or FreeRTOS. This chapter offers a road-map for the design of real-time embedded systems evaluating the pros and cons of the different programming languages and operating systems. Organization: This chapter is organized in the following way. Section 2 describes the main characteristics that a real-time operating system should have. Section 3 discusses the scope of some of the more well known RTOSs. Section 4 introduces the languages used for real-time programming and compares the main characteristics. Section 5 presents and compares different alternatives for the implementation of real-time Java. Finally, Section 6 concludes.