A Survey Of Embedded Operating System

A Survey of Embedded Operating System

Catherine Lingxia Wang, Bo Yao, Yang Yang, Zhengyong Zhu

Abstract

This paper presents a survey of several major embedded operating systems. It analyzes several design

issues of embedded operating system, such as architecture, memory management, IPC, process

management, network support, and the impact of hardware limitation and application requirement of

embedded system.

We analyzed three prevailing embedded operating systems: Windows CE, embedded Linux and QNX.

Finally we gave an overview on the considerations why these decisions are made.

Introduction

Embedded system is application-oriented special computer system which is scalable on both software and

hardware. It can satisfy the strict requirement of functionality, reliability, cost, volume, and power

consumption of the particular application.

With rapid development of IC design and manufacture, CPUs became cheap. Lots of consumer electronics

have embedded CPU and thus became embedded systems. For example, PDAs, cellphones, point-of-sale

devices, VCRs, industrial robot control, or even your toasters can be embedded system. There is more and

more demand on the embedded system market. Some report expects that the demand on embedded CPUs is

10 times as large as general purpose PC CPUs.

As applications of the embedded systems become more complex, the operating system support and

development environment became crucial. In this paper, we mainly analyze three major embedded

operating systems, QNX 4 RTOS, Windows CE and embedded Linux. Windows CE and embedded Linux

are most widely used embedded operation systems. QNX is a relatively simple one and can fit in some

simple applications.

QNX 4 RIOS

The QNX 4 RTOS is developed by QNX Software Systems Ltd. for the applications in consumer

electronics, telecommunications, automotive systems, medical instrumentation which need high reliability,

superior performance, sophisticated functionality, and massive scalability. It's small, scalable, extensible,

and fast. A number of design innovations were developed for QNX 4 RTOS to deliver the full performance

of the hardware, which also help us to look in the impact of embedded system hardware limitation on the

OS design.

Embedded Linux

In the past two years, Linux has become popular on embedded devices—especially consumer gadgets,

telecom routers and switches, Internet appliances and automotive applications.

Because of the modular nature of Linux, it is easy to slim down the operating environment by removing

utility programs, tools, and other system services that are not needed in an embedded environment. You

can strip the standard Linux kernel to the barest as needed. One of the major advantages of Linux is that it

is a fully functional OS, with support for network that is becoming a very important requirement in

embedded systems because people need to "compute anywhere, anytime". Because you can add or unload

modules from the kernel at runtime, this makes embedded Linux very flexible. It is more encouraging that

the Linux code is widely available, portable to any processor, scalable and stable. Because it is open, Linux

doesn't require the user to pay license fees or royalties—particularly important to developers of consumer

electronics, who have narrow margins.

Windows CE

Windows CE is first introduced in the Handheld PC (H/PC) set of products in November 1996. But later

became a highly configurable operating system after Microsoft released the windows CE OEM Adaptation

Kit in March 1997. Several advantages for Windows CE includes a subset of the Win32 API that addresses

the most commonly needed services, a low overhead device driver model and built-in power management.

Windows CE can be ported to a broad range of business, consumer and industrial devices. The application

of Windows CE includes consumer electronics like handheld PC, AutoPC, video game player and digital

camera, and industrial products like barcode reader and programmable logic controllers.

Comparison

1. Hardware specification

There are various hardware platforms for embedded system. The most popular ones include x86, MIPS,

PowerPC，Hitachi SH, PowerPC and Strong Arm processors. On one hand, the embedded operating

systems are adapted to run on most of the processor available to embedded system. On the other hand, they

also have some own restrictions.

Processor

QNX can run on all generic x86-based processors (386 and up).

Linux is currently available to run on virtually every general-purpose microprocessor and to support the

most common processors used in the embedded world, including the ARM, Strong Arm, MIPS, Hitachi SH,

Motorola/IBM PowerPC, and x86-compatible families. EHOE vendors, such as Red