Designing Embedded Hardware

Ethernet

Anyone even remotely involved with computers has heard of Ethernet. Developed at Xerox PARC^[16] in the early 1970s, this local area networking standard has found its way into every possible application and has evolved over time to encompass a number of standards ranging from wireless networks (802.11) to gigabit Ethernet.

In this section, I’ll look at how you add a simple Ethernet interface to your embedded computer. We will develop a 10Mbps interface only, as higher-speed interfaces require special attention to PCB design and EMC issues. So, for your sake of ease and reliability, we’ll keep it simple and low speed.

The Ethernet standards and protocols are detailed in Ethernet: The Definitive Guide by Charles E. Spurgeon, available from O’Reilly & Associates. This excellent book gives definitive coverage of Ethernet and is a must for anyone developing Ethernet-based hardware. It is essential background reading.

By adding Ethernet to your embedded system, you gain access to a network and all the possibilities that brings. You can send data to a host computer at high speed and access printers, file servers, databases, and even the Internet. You can also monitor and control your embedded system from afar or even have it send you email when it needs attention. Take an AT90S8515 AVR and add an Ethernet interface and some high-capacity flash memory, and you have yourself a simple web server. Add an ADC and some sensors, and your web server becomes a weather station showing current ...