Barr Michael - Programming Embedded Systems

Copyright 2009 O'Reilly Media, Inc.

If you mention the word embedded to most people, theyll assume youre talking about reporters in a war zone. Few dictionariesincluding the canonical Oxford English Dictionary link embedded to computer systems. Yet embedded systems underlie nearly all of the electronic devices used today, from cell phones to garage door openers to medical instruments. By now, its nearly impossible to build anything electronic without adding at least a small microprocessor and associated software.

Vendors produce some nine billion microprocessors every year. Perhaps 100 or 150 million of those go into PCs. Thats only about one percent of the units shipped. The other 99 percent go into embedded systems; clearly, this stealth business represents the very fabric of our highly technological society.

And use of these technologies will only increase. Solutions to looming environmental problems will surely rest on the smarter use of resources enabled by embedded systems. One only has to look at the network of 32-bit processors in Toyotas hybrid Prius to get a glimpse of the future.

Though prognostications are difficult, it is absolutely clear that consumers will continue to demand ever-brainier products requiring more microprocessors and huge increases in the corresponding software. Estimates suggest that the firmware content of most products doubles every 10 to 24 months. While the demand for more code is increasing, our productivity rates creep up only slowly. So its also clear that the industry will need more embedded systems people in order to meet the demand.

What skills will these people need? In the PC world, one must be a competent C/C++ programmer. But embedded developers must have a deep understanding of both the programming languages and the hardware itself; no one can design, code, and test an interrupt service routine, for instance, without knowing where the interrupts come from, how the hardware prioritizes them, the tricks behind servicing that hardware, and machine-level details about saving and preserving the systems context. A firmware developer must have detailed insight into the hardware implementation of his systems peripherals before he can write a single line of driver code.

In the PC world, the magic of the hardware is hidden behind an extensive API. In an embedded system, that API is always written by the engineers that are developing the product.

In this book, Michael Barr and Anthony Massa show how the software and hardware form a synergistic gestalt. They dont shy away from the intricacies of interrupts and I/O, or priority inversion and mutexes.

The authors appropriately demonstrate building embedded systems using a variety of open source tools, including the GNU compiler suite, which is a standard tool widely used in this industry. eCos and Linux, both free/open source products, are used to demonstrate small and large operating systems.

The original version of this book used an x86 target board, which has been replaced in this edition by an ARM-based product. Coincidently, as this volume was in production, Intel made an end-of-life announcement for all of its embedded x86 processors. Readers can be assured that the ARM will be around for a very long time, as its supported by an enormous infrastructure of vendors.

The hardware is inexpensive and easily available; the software is free. Together they represent the mainstream of embedded systems development. Readers can be sure theyll use these tools in the future.

Buy the development kit, read the book, and execute the examples. Youll get the hands-on experience that employers demand: building and working with real embedded applications.

Jack Ganssle