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XML embedded Web support eases design

Posted: 17 Nov 2003 ?? ?Print Version ?Bookmark and Share

Keywords:xml? web page? web server? embedded device? os?

XML is rapidly becoming the technology of choice for interfacing embedded systems to applications. There are many approaches to implementing XML-capable, Web-enabled embedded devices, ranging from software to dedicated hardware. Perhaps the simplest method - though most costly in terms of sucking up precious processing power - is supporting the Web processes completely in external software. Here, it is possible to apply the capabilities of an embedded OS such as Microsoft's Windows CE.

However, designers of resource-constrained embedded projects will find that a more efficient approach is to implement Web support directly in hardware. Options for such an approach range from full 32bit processors plus Web servers, to cost-efficient hybrid solutions that combine lower power drains with high data throughput.

Currently, Web support is available for most major embedded architectures, including Z80, MIPS, ARM, X86 and others. Since thousands of different off-the-shelf embedded ICs exist, support options vary, so designers should investigate; sometimes it is software only, and often an external board is required to handle the network connection. Web support can be most cost-effective when the most important hardware component required for Web support - the Ethernet controller - is included on the chip.

Web support implemented on an embedded processor differs from a Web server running on the PC architecture. In contrast to the standard PC and Internet-based Web setup, where Web pages are maintained on a mass-storage device such as a disk drive, the Web pages created by an embedded processor are accessed as embedded data elements. Resources for an embedded implementation are constrained, both in terms of memory and power. An XML-capable, Web-enabled embedded system has got to be leaner, meaner and smarter than its bloated PC counterpart.

One benefit of folding Web support into an embedded application is that it frees engineers from the time-consuming burden of user-interface design. That is because embedded Web pages, written in HTML/XML and converted to C/C++ code, provide ready-made user-friendly interfaces that have the ability to support complex embedded systems.

XML provides a processor-independent way of encoding data for interchange between diverse systems. It uses defined tags to place coded definitions inside Web pages. Designers are developing different sets of tag definitions for different application environments that use XML syntax. For example, available tag sets include vocabularies for electrical engineering, e-commerce, multimedia data and straight document info.

It is possible to transmit XML documents to and from other systems in a number of ways. For one, they can travel as HTTP objects. This means that support for Web services such as Simple Object Access Protocol or XML-RPC must be incorporated into the server.

Including XML and HTML support in embedded systems requires special provisions in the software tools chain. Specifically, the compiler-linker tied to the embedded part must be designed to allow the XML code to be embedded within the application program's C-language or assembly code.

In the real world, accessing the XML capability is fairly easy - the programmer incorporates a bunch of "#include" statements into his or her programmer. Many developer's suites include sample HTML/XML pages, a feature which greatly simplifies any project.

- Dick Jensen

Director, Development Tool Platforms

Zilog Corp.





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