Java for embedded systems

Java requires infrastructure to run on embedded devices. This requirement must be traded against the powerful support for dynamic behavior that it offers embedded system developers     

EJVM: an economic Java run‐time environment for embedded devices

As network‐enabled embedded devices and Java grow in their popularity, embedded system researchers start seeking ways to make these devices Java‐enabled. However, it is a challenge to apply Java technology to these devices due to their shortage of resources. In this paper, we propose EJVM (Economic Java Virtual Machine), an economic way to run Java programs on network‐enabled and resource‐limited embedded devices. Espousing the architecture proposed by distributed JVM, we store all Java codes on the server to reduce the storage needs of the client devices. In addition, we use two novel techniques to reduce the client‐side memory footprints: server‐side class representation conversion and on‐demand bytecode loading. Finally, we maintain client‐side caches and provide performance evaluation on different caching policies. We implement EJVM by modifying a freely available JVM implementation, Kaffe. From the experiment results, we show that EJVM can reduce Java heap requirements by about 20–50% and achieve 90% of the original performance. Copyright © 2001 John Wiley & Sons, Ltd.     

Extending an embedded RISC microprocessor for efficient translation based Java execution

Java has gained great popularity in embedded appliances such as set-top boxes, smart phones and other hand held devices. In this paper we propose a translation based hw/sw codesigned Java virtual machine architecture, which extends a typical embedded RISC processor. The architectural extensions we propose include special instructions that accelerate translated blocks dispatch and security checks for arrays and objects. The extensions are done in a way that operating systems support is maintained, something that makes their adoption more attractive. Benchmarking using Embedded Caffeine Mark (ECM) benchmarks, showed significant speedups, especially when high performance RISC processors are employed.     

CALEE: A computer-assisted learning system for embedded OS laboratory exercises

With the popularity of embedded systems and the consequently rising demand in the job market for professionals well-versed in them, embedded operating systems (EOSs) have become one of the core courses in computer science studies across the world. The objective of EOS courses is to develop students' ability to port, modify, and customize an embedded operating system through a series of laboratory exercises. However, our teaching experience has revealed that beginners require a considerable amount of time to familiarize themselves with the development environment and the relevant processes, such as operating in a command line interface, setting environment variables, and kernel configurations. Furthermore, students need to constantly handle compiler error messages, malfunctions of the target EOS, and incompatibility issues related to development tools. These problems may frustrate and discourage students. A common strategy to address this problem is to dedicate more hours to teaching or to hire more teaching assistants to help students progress. However, none of these methods is suitable for institutions with limited resources. Therefore, in this paper, we develop a computer-assisted learning system called the Computer-assisted Learning Environment (CALEE) to assist students with their assignments and thus motivate them. CALEE consists of two parts: a self-learning assistant (SLAT) and a collaborative learning website (CLW). SLAT is a software application that provides a set of useful functions to help students perform EOS laboratory exercises, whereas the collaborative learning website seeks to encourage greater interaction among students. Our experiments show that CALEE expedites learning, improves students' motivation, and reduces the teaching load.     

嵌入式网络报警系统的研究与实现

通过在嵌入式系统中应用实时操作系统、TCP/IP协议、网络互连等技术,构建了一套基于ARM微处理器的嵌入式网络报警系统。重点介绍了各技术要点的实现过程,为各种技术的融合应用提供一个可行的实例。     

嵌入式Linux防火墙系统研究与实现

为了构建安全可靠的网络,同时降低使用防火墙的成本,对Linux2.4内核防火墙结构Netfilter的实现机制进行了深入的研究和分析,并利用该机制设计实现了一个嵌入式Linux防火墙系统,该防火墙实现完善了包过滤、URL过滤、NAT和日志等防火墙基本功能,同时集成了非军事区（DMZ）,为Internet和Intranet之间建立了缓冲地带,以保证Intranet的安全。此外,该防火墙系统还集成了状态检测技术,可在内存中维护一个跟踪连接状态的表,比简单包过滤防火墙具有更大的安全性,并提供友好的管理配置界面。     

An interface test model for hardware-dependent software and embedded OS API of the embedded system

An embedded system has a hierarchical structure including hardware-dependent software layer, operating system layer, and applications layer. Since the system has interfaces between the different layers that are tightly coupled and inter-dependent to each other, these interfaces are the focal area to be tested.This paper proposes an Embedded System's Interface Test Model (EmITM) to test hardware interfaces and OS interfaces. The EmITM provides a set of test items based on the interfaces when testing embedded software. We apply our model to embedded software test and analyze the test results.     

嵌入式网络视频服务器的设计

随着计算机技术、网络技术、图像处理技术和嵌入式技术的发展，基于嵌入式和Intemet的视频监控系统成了监控系统的主流。介绍了以S3C4510B为核心的嵌入式网络视频服务器的硬件构成及实现方法。应用软件是实现嵌入式系统功能的关键，建立在pCLinux操作系统上，着重阐述了视频服务器软件的设计方法。     

无线传感器网络操作系统关键技术研究

针对无线传感器网络的特点分析了无线传感器网络对操作系统的特殊需求,分析了无线传感器网络操作系统的特点.重点介绍了无线传感器网络操作系统开发过程中的几大关键技术:结构的层次化技术、框架技术、节能型通信模型技术、可裁减构件技术、普适计算模型技术.这些技术已用于西北工业大学的无线传感器网络的开发实践中,并取得了较理想的效果,对更好地开发无线传感器网络操作系统和开发应用软件有很高的参考价值.     

Energy consumption analysis for two embedded Java virtual machines

In this paper we present a general framework for estimating the energy consumption of an embedded Java virtual machine (JVM). We have designed a number of experiments to find the constant overhead and establish an energy consumption cost for individual Java opcodes for two JVMs. The results show that there is a basic constant overhead for every Java program, and that a subset of Java opcodes have an almost constant energy cost. We also show that memory access is a crucial energy consumption component.     

嵌入式JAVA虚拟机的加速改造

首先分析了Sun公司的嵌入式Java虚拟机KVM性能低效的原因,在此基础上引入两种Java虚拟机性能加速技术:JIT和Native线程。通过建立MVM模型,将这两种加速技术融合到了Java虚拟机中,并详细介绍了实现这两种加速技术的关键数据结构和算法。实验结果表明Java虚拟机的性能获得明显的提高。     

基于CPCI总线的嵌入式计算机通用接口设计

针对基于CPCI总线的嵌入式计算机设计中遇到的底层驱动软件与具体硬件芯片相互关联的问题,开展了嵌入式计算机通用接口设计的研究.采用软件、硬件与现场可编程技术相互结合的设计方法,通过通用硬件接1:1电路设计、共享存储区设计、通用函数设计,实现了基于CPCI总线的嵌入式计算机通用接口,并成功应用于具体的工程实践.     

嵌入式可信计算机研究

将可信计算技术应用到嵌入式系统中,是一条有效解决嵌入式设备安全问题的新思路.首先阐述将可信计算与嵌入式技术相结合的趋势,然后分析了该技术所面临的诸多挑战,并给出了将CRTM集成到嵌入式TPM中实现的嵌入式可信计算机体系结构,最后分别从信任根和信任链两方面提出了满足嵌入式系统需求的详细设计方案.     

PC104计算机网络通讯系统设计与研究

本文介绍了基于DOS操作系统下嵌入式PCI04计算机的UDP网络通讯的实现基理，重点提出了如何解决不可靠的、非面向连接的UDP通讯丢帧问题。给出了实际某火控系统中UDP网络通讯的硬件设计和部分软件代码、相关流程图.     

基于MicroBlaze的PetaLinux嵌入式操作系统移植

近年来,SoPC(System On a Programmable Chip,可编程片上系统)的应用日益增多。针对此趋势,系统介绍了Xilinx公司的MicroBlaze软核处理器和PetaLinux操作系统的特点,利用EDK开发套件搭建一个基于MicroBlaze的硬件平台,并研究了PetaLinux的移植、自定义设备驱动的添加、配置和启动。实验证明,使用PetaLinux开发的SoPC能够满足用户复杂多变的需要,且构建简单、快速,缩短了产品的开发周期。     

Linux虚存机制在嵌入式系统背景下的分析

在嵌入式应用领域里，从因特网设备到专用控制系统，Linux操作系统前景都很光明，但Linux虚拟内存管理机制对于一个嵌入式系统来讲往往是多余的，更重要的是影响系统的实时性能，对Linux的虚拟内存管理机制进行了分析，并从源码级提出了一种改进方案，以适用于嵌入式Linux。     

Efficient exception handling in Java bytecode-to-C ahead-of-time compiler for embedded systems

One of the most promising approaches to Java acceleration in embedded systems is a bytecode-to-C ahead-of-time compiler (AOTC). It improves the performance of a Java virtual machine (JVM) by translating bytecode into C code, which is then compiled into machine code via an existing C compiler. One important design issue in AOTC is efficient exception handling. Since the excepting point and the exception handler may locate in different methods on a call stack, control transfer between them should be streamlined, while an exception would be an “exceptional” event, so it should not slow down normal execution paths. Previous AOTCs often employed a technique called stack cutting based on a setjmp()/longjmp() pair, which we found is involved with too much performance overheads. Also, when the AOTC and the interpreter are employed concurrently (e.g., some methods are AOTCed while other methods are interpreted), the performance of normal execution paths is affected more seriously. This paper proposes a simpler solution based on an exception check after each method call, merged with garbage collection check for reducing its overhead. Our evaluation results on SPECjvm98 on Sun's CVM indicate that our technique can improve the performance of stack cutting by more than 25%. A similar performance benefit can be noted on a hybrid execution environment of both the AOTC and the interpreter.     

采用Java ME测试Agent的嵌入式设备自动测试框架

提出了一个将手工测试转换为自动测试的轻量级框架。经过扩展Java ME API,Java ME程序（MIDlets）具备拦截和模拟用户输入能力。Java ME测试Agent建立HTTP服务,根据配置文件或Web浏览器控制命令决定工作方式：学习模式或测试模式。在学习方式,Agent根据用户输入生成测试脚本;在测试模式,Agent利用测试脚本模拟测试。在GPS/PDA上实现了测试框架并用实验验证。该解决方案用模拟自动测试代替手工费时费力交互手工测试,提高了测试效率。