Choice Versus Default

by Steve Ciarcia

suppose that everything we do can be rationalized to being a matter of choice or default. Do we bother to learn a new task or expand our expertise if we don't have to? How significant must the benefits of doing something a new way be for us to make an effort to learn it?

Let me share a humorous example. My 10-year-old grandson bounded into our house recently. After the usual hugs and pleasantries, he reverted to being a typical adolescent. After conning me out of new batteries for his Gameboy, he piped an urgent imperative, "What time is it? I can't miss Stone Cold Steve Austin!"

I looked at the wall clock that was barely 15' away and noted the time was 4:37 p.m. Becoming a facilitator for the WWF wasn't something I would do easily. I pointed at the wall clock rather than simply answering. He looked at the clock. Surprisingly, instead of reading the time, he jumped up and ran into the guest bedroom where he usually stays when visiting. At the conclusion of his round-trip dash, he plopped back in the kitchen chair and said with a sigh of relief, "It doesn't start for another hour. I hope we're having dinner early."

Having kids around is a new thing for me. People who survived parenthood warned me that I should neither react immediately to what kids say nor look at every situation like it was supposed to be a learning situation for the kid. As for the WWF and me, we'll have to remain in a state of mutual coexistence.

It only took me a few seconds to realize what was going on here. The wall clock I pointed at in the kitchen is analog-the big hand and little hand deal. The clock in the bedroom is digital. Was the answer that simple? Trying not to be the condescending grandparent, I pointed at the kitchen wall clock and said, "Hey, kid?" (I affectionately called him kid when I'm trying to make a point), "Can you read that?"

"If I study it, I can usually figure it out. I just thought I'd save time by reading the clock in the bedroom. I can't miss Steve Austin, you know," he answered.

I won't bore you with the details after that. Let's just say that it demonstrated his level of necessity wasn't great enough to choose an unfamiliar technique when, with a little more effort, there was a default approach. Unfortunately, this lesson made me consider whether or not my concept of choice versus default needed modification too.

At least for electronics people, this experience parallels using digital versus analog design solutions. I don't mean obvious digital functions like encryption or combination logic. I mean real analog I/O, traditionally done with external analog circuitry attached to a processor, versus synthesized analog functions using mostly digital means. A typical example of this is a ramp generator. You can do it with an op-amp. You can also do it with a processor and a DAC. The question is, which method would you choose these days, and what issues influence your decision?

Just like calculators have reduced tedious hand calculation, today's technology strives to meet the demand. Newly designed programmable analog architectures attempt to make analog interfacing more comfortable for digital designers. The only saving grace is that at least for now, programmable components aren't presented as a way for designers to avoid understanding real analog interfacing issues. Not everything can nor should be done with digitally programmable devices. Things like signal amplification and filtering are still less expensive and less power hungry using an analog approach.

Design architecture is not black or white. Cost and design finesse may not even enter the equation. These days, often the only necessity is product delivery. Over the years, I've been critical of the fact that fewer engineers have traditional analog design experience. I also believe there is a tremendous gray area in design issues that can justify virtually any approach that succeeds (that's the only way I can rationalize using an embedded PC where an 8051 could do the job).

Nonetheless, design technique should be an informed choice and never a consequential default. Our subtitle is "The Magazine for Computer Applications". Sometimes this means describing analog, as well as digital designs. Other times it means describing overkill instead of finesse. Regardless of the subject, I want you to know that our real message is always helping you have an educated choice rather than merely the default.