Designing Embedded Hardware, 2nd Edition

Printed-Circuit Boards

Printed-circuit boards (PCBs) are epoxy-bonded fiberglass sheets plated with copper. The copper plating is etched away, leaving tracks (traces) that form the interconnections of the circuit (Figure 6-23). PCBs are very reliable and are the only realistic option if you intend to produce more than one system. It is possible to etch your own PCBs, but commercial PCB production isn't that expensive, and it is worth the cost to get professionally produced boards.

Figure 6-23. PCB for a PIC-based model train controller (Chapter 14)

EDA (Electronic Design Automation) software is used to create the schematic and PCB design. The most popular EDA software comes from Mentor Graphics (http://www.mentor.com) and Protel (http://www.protel.com). There is also a gnu (http://www.gnu.org) PCB editor, called PCB, which is freely available. Such programs normally come with several tools, allowing schematic entry, netlist generation (a list of what needs to be connected to what), PCB layout, manual routing (making the connections), and autorouting. There's a great temptation to use autorouters, as they simplify the process of generating the PCB by getting your workstation to do the hard work of routing. However, I prefer to lay out the circuit board myself. (I've seen some autorouters make a real mess of a design.) Routing the board manually can take a long while, but ...