Issue 99, October 1998
X-Y Graphing Data Logger

USING COMPONENETWARE

Componentware is a popular buzzword in the IT community. It stands for software entities (sometimes as big as a full-featured word processor) that you can reuse as building blocks for other programs without having to know too many details.

What does componentware have to do with hardware design? A lot. A 16 ´ 2 LCD, an RF tuner, and a stamp-sized controller (e.g., Basic Stamp, Domino, PicStic, or Basic Tiger) comprise the hardware counterpart of componentware techniques.

Once upon a time, we had libraries of subcircuits that worked well. But today, we have fat, white-box components. The list goes on to include DC-to-DC converters, modem on a chip, LCD voltmeters, wall-wart power supplies, and even a whole PC!

Is the componentware a good design technique? I think so. When you have a 16 ´ 2 LCD, you don’t need to know the details about LCD polarizers or backlighting problems. Just leave these problems to LCD specialists, and concentrate on your specific application.

Adding components together increases the abstraction level and, consequently, the designer’s freedom and power. With so many problems already solved, you can concentrate on solutions to new problems.

All of this comes at no extra cost. Most white-box components are derived from high-volume consumer devices. Everyone benefits from the optimized price, industrial quality, uniformity, and reduced time to market.

In this design, I go a step further and use a graphic calculator as a white-box component to build a data logger. Admittedly, thinking of a pocket calculator as a component is a little wild, and we may never see such a component as a standard.

Nevertheless, the general approach is effective, and the benefits can apply to a number of designs. For one thing, it increases designer power, putting a graphical LCD, a programming language, lots of memory, and PC connectivity at your disposal.

Using a calculator also cuts development time, so it takes just days (not weeks or even months, if you include the calculator math) to go from ideas to prototype. This technique also simplifies the problem-solving path: a simple concept, simple electronics, and simple software yield a complex result.

You also get lower power consumption (at least 200 h on standard batteries), which is more than 20 times a comparable PC-based solution.

Also, using the calculator cuts cost. Just one, off quantity, sells for the price of an LCD alone. Overall costs are more than 20 times less than any PC-based solution of comparable power.

You get increased flexibility, low cost, and an easily replaceable flash-reprogrammable input board, enabling you to retain the calculator. Plus, only data acquisition and transmission need to be tested, and you save on production costs because you don’t need complicated plastics and electronics.

Documentation is simpler, too. Just add a "Capturing data" chapter to the calculator’s manual.

Size and weight are also reduced. Even prototypes are handheld, weighing only 290 g (including batteries), and series production sizes can be reduced further.