Real-time operating systems for embedded computing

ACM SIGSOFT Software Engineering Notes, 2007

Hard real-time embedded systems have stringent timing constraints that must be met in order to ensure the correct functioning of the system. In many cases, these systems are composed of several CPU-bound tasks, which may need to rely on multiple processors, since just a single processor may not allow meeting all timing constraints. In order to deal with stringent constraints, specialized operating system kernels are often adopted in real-time embedded systems. However, the operating system usage may introduce significant overheads in execution time as well as in memory requirement. Software synthesis is an alternative approach to operating systems usage, since it can generate tailored code that satisfy: (i) functional, performance, and resource constraints; and (ii) other features such as scheduling, resource management, communication and synchronization. In this paper, a software synthesis approach based on a formalism, namely, time Petri nets, is presented in order to generate pre...

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.

Languages for System Specification, 2004

With the increasing complexity of the emerging embedded real-time systems, traditional design approaches can not provide sufficient support for the development of these systems anymore. They especially lack the ability to trace and analyse real-time system properties. In this paper, we investigate the design difficulties for embedded real-time systems and propose several principles for coping with these difficulties, which should be incorporated by an "adequate" design approach. Several prevailing design approaches are evaluated against these principles and their merits and drawbacks are examined and illustrated by examples. Finally, a platform-independent approach (POOSL[vdPV97, Gei02] + rotalumis[vB02]) is introduced to remedy these design problems for embedded real-time systems. Initial experiments have been performed that confirm the advantages of this approach.

1997

Abstract Embedded systems are typically implemented as a set of communicating components some of which are implemented in hardware and some of which are implemented in software. Usually many software components share a processor. A real-time operating system (RTOS) is used to enable sharing and provide a communication mechanism between components. Commercial RTOSs are available for many popular micro-controllers.

IEEE International Conference on Computer-Aided Design, 1998

Summary form only given. Embedded DSPs and CPUs are already commonplace in board-level systems and are becoming increasingly popular on systems-on-silicon. As embedded software grows in size and complexity, real-time operating systems [(RTOSs) are required to manage the embedded processor and ensure real-time response. This tutorial will introduce the attendee to real-time operating systems for embedded computing and their use in the design of embedded software. with both basic principles and advanced practice.

2001

finished. It is possible to avoid the problem by adding break points to the event handling code where the handling of urgent events can take place. On the other hand, the problem is not critical, if a powerful processor is available. The real-time properties of most embedded systems are based on the use of real-time operating systems. Application of such operating systems requires high expertise and much time. The resulting software is often heavy and hard to maintain. In this paper we present a class of application specific operating systems called ReaGOS. ReaGOS is based on a new architecture and an operating principle, where the operating system calls application programs but not vice versa. The new architecture saves both data and code memory and it is fast enough for embedded systems. The operating system is generated automatically from a high level graphical specification. Another method uses interrupt mechanisms to handle I/O driver events [5]. This method has some disadvanta...

EURASIP Journal on Embedded Systems, 2008

The rapid progress in processor and sensor technology combined with the expanding diversity of application fields is placing enormous demands on the facilities that an embedded operating system must provide.

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.

2004

Embedded systems can no longer depend on independent hardware or software solutions to real time problems due to cost, efficiency, flexibility, upgradeability, and development time. System designers are now turning to hardware/software co-design approaches that offer real time capabilities while maintaining flexibility to support increasing complex systems. Although long desired, reconfigurable technologies and supporting design tools are finally reaching a level of maturity that are allowing system designers to perform hardware/software co-design of operating system core functionality such as time management and task scheduling that allow the advantages of higher level program development while achieving the performance potentials offered by execution of these functions in parallel hardware circuits.

An RTOS is a software component that is used in the majority of the real-time embedded systems. It has a significant effect on the system's performance and reliability. This paper addresses the issue of publishing parameterized performance characteristics of an RTOS in a platform independent manner. Concepts of parametric timing analysis were extended to consider the performance of the processor, memory and peripherals in a parameterized way. The proposed method was applied to a commercial RTOS. Validation of the method shows results with a precision better than 10%. Key-words: timing analysis, WCET (Worst Case Execution Time), RTOS (Real-Time Operating System) performance characterization, COTS (Commercial Off The Shelf) software component performance.