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From the Introduction to
Embedded Ethernet and Internet Complete
Embedded Ethernet and Internet Complete is a guide to designing and programming embedded systems to communicate in local Ethernet networks and on the Internet.
An embedded system is a device that has computer intelligence and is dedicated to performing a single task, or a group of related tasks. Embedded systems often perform monitoring and control functions such as gathering and reporting sensor readings or controlling motors and switches. They’re called embedded systems because the program code is an integral part of, or embedded in, the devices.
Ethernet is the networking technology used in many offices
and homes to enable computers to communicate and share resources. Many
Ethernet networks also connect to a router that provides access to the
Internet.
For many years, embedded systems and Ethernet networks existed in separate
worlds. Ethernet was available only to desktop computers and other large
computers. Embedded systems that needed to exchange information with
other computers were limited to interfaces with low speed, limited range,
or lack of standard application protocols.
But developments in technology and the marketplace now make it possible for embedded systems to communicate in local Ethernet networks as well as on the Internet. Network communications can make an embedded system more powerful and easier to monitor and control. An embedded system can host a Web site, send and receive e-mail, upload and download files, and exchange information of any kind with other computers connected via a network interface.
One development that has made Ethernet feasible for embedded systems is the availability of inexpensive controller chips to handle the details of Ethernet communications. The CPUs that provide the processing power for embedded systems have also gotten faster and more capable of handling the demands of communicating with the controllers. Internet protocols provide standard, well-documented ways of exchanging data. Both Ethernet and the Internet protocols are free and open standards available for use without royalties or licensing fees.
Technologies and Protocols
Designing and programming an embedded system for networking can require skills and knowledge in a variety of areas in electronics, programming, and networking.
To interface an Ethernet controller to a CPU, you’ll need to know about hardware design.
To write the program code that controls the system, you’ll need to know how to write and debug code for your system’s CPU.
To build the network, you’ll need to know how to select and use cables, repeater hubs, switches, and other network hardware.
To enable sending and receiving data over the local network,
you’ll need to be familiar with the Ethernet protocol.
To enable sending and receiving data over the Internet
and some local networks, you’ll need to be familiar with Internet
protocols.
To serve Web pages, you’ll need to know about Web-page
design.
To keep your system and its data safe, you’ll need
to know how to implement measures that provide network security.
This book brings together all of these fields of knowledge
with a focus on how they relate to the networking of embedded systems.
Creating a Web page for a major corporation’s Web site is very
different from creating a home page for a device with limited resources.
But designing for small systems isn’t just a matter of scaling
back. For example, a Web page hosted by an embedded system will almost
certainly want to display more than basic pages with static, unchanging
text. Instead, the pages typically provide real-time information and
may want to accept and act on user input as well.
This book shows how to meet the networking and application
needs of embedded systems in spite of their hardware and software limitations
of small devices. In many cases, you can choose to simplify the tasks
involved by using hardware and software modules that do much of the
work for you.
Who should read this book?
This book is for anyone who wants to design, program,
or learn about networking with embedded systems.
These are some of the questions this book answers:
What are the advantages and limits of using Ethernet with
embedded systems? Find out whether Ethernet is the right technology
for your project.
What hardware and program code do I need to connect an
embedded system to an Ethernet network? There are many options for creating
an Ethernet-capable embedded controller, from buying a module with hardware
and software support for networking to putting it all together from
scratch. This book will help in selecting the components for your systems.
How do I build a network? An Ethernet-capable device can’t
communicate if it doesn’t have a network to connect to. Find out
how to select network cables and hubs and use them to put together an
Ethernet network
How can I connect my device or network to the Internet?
An Internet connection can extend a device’s reach to the entire
Internet. Find out how to obtain an Internet connection for your device
and ensure that your network is configured to enable your device to
perform the communications it requires.
How can my devices send and receive messages over the
local network or the Internet? The Internet and many local networks
use the TCP/IP suite of Internet protocols to send and receive messages
of all types. This book will show you how embedded systems can use these
protocols to exchange messages.
How can I host a Web site on my embedded system? Even
a very basic embedded system can function as a Web server, which responds
to requests from other computers for Web pages. Find out what a device
requires to function as a Web server and how to create the pages your
device will serve.
How can my Web server’s pages include dynamic, real-time
content and respond to user input? This book will show how an embedded
system can display up-to-date information and respond to text and other
input from users.
How can my embedded system send and receive e-mail, exchange
files with an FTP server, or host an FTP server that other computers
can access? This book includes examples for each of these applications.
How can I ensure that the programming and other information
in my devices is secure on the Internet? Good security practices can
ensure that unauthorized users can’t change configuration settings
or view private information in your device. Security practices can also
help to prevent problems due to careless or accidental mistakes. Find
out what you need to do to keep your device and the local network it
resides in secure and functioning properly.
This book assumes you have a basic knowledge of digital
circuit design and microcontroller or microprocessor programming for
embedded systems. I don’t assume any knowledge of networking.
About the Example Applications
The example applications in this book use two Ethernet-capable
modules: a TINI module from Dallas Semiconductor and a RabbitCore module
from Rabbit Semiconductor. Both are capable and well-supported products
that will enable you to get your projects up and running quickly. You
won’t go wrong using either of these modules.
The TINI examples use the Java programming language. The
Rabbit examples use Dynamic C, Rabbit Semiconductor’s implementation
of the C programming language for embedded systems. Every application
in the book has both a TINI and RabbitCore example. The book also discusses
a number of other components that are suitable for many projects.
How This Book Is Organized
Each of the chapters in this book has two sections: Quick Start and In Depth.
The Quick Start section gives practical information and
examples that you can put to work right away. The In Depth section has
more detail about the protocols and technologies used in the Quick Start
examples.
The order that you read the sections may vary depending on your needs and preferences. You can read the book straight through for an understanding of each of the topics in turn. Or to get something up and running quickly, you might read the Quick Start sections first, referring to the In Depth material as needed. Or if you prefer to gain a background in a topic before delving into implementation details, you can read a chapter’s In Depth section before the Quick Start.