Designing Embedded Hardware

Quick-and-Dirty Construction

It is possible to build very simple circuits by just soldering the components together in free space. For example, with the AVR design in this chapter, the leads of the watch crystal can be soldered directly onto the pins of the processor, with the crystal lying across the top of the processor. Wires are soldered onto the pins bringing in ground and power and connecting the processor’s I/O to the outside world. This technique is variously referred to as “a rat’s nest,” a “bird’s nest,” or “what the hell is that?”

This is a quick-and-dirty method, useful for rapid prototyping of extremely simple circuits. It’s not really recommended, but you can get away with it in a pinch. Don’t try it with anything that is even slightly complicated or running at any reasonable speed. If you do, you’ll spend more time debugging the construction than debugging the actual design or code!

Breadboarding

Breadboards are plastic blocks with arrays of holes. They are designed to hold DIP-packaged integrated circuits and discrete components. The term “breadboard” dates back to the olden days when valve radios were constructed on a base of solid wood (a cutting board for bread). The term has stuck, and the modern breadboard can still be found in electronics hobbyist stores and even the occasional university teaching lab.

While it is possible to build very low-speed microprocessor systems and general digital circuits on breadboards, try not to. There be dragons! As a general rule, ...