Page 41 - The Art of Designing Embedded Systems

28 THE ART OF DESIGNING EMBEDDED SYSTEMS

3. Defects are a sure measure of customer-perceived quality. Once a
product ships, we’ve got to log defects to understand how well our
firmware processes satisfy the customer-the ultimate measure of
success.
But first, a few words about “measurements.”
It’s easy to take data. With computer assistance we can measure just
about anything and attempt to correlate that data to forces as random as
the wind.
W. Edwards Deming, 1900-1993, quality-control expert, noted that
using measurements as motivators is doomed to failure. He realized that
there are two general classes of motivating factors: The first he called “in-
trinsic.” These are things like professionalism, feeling like part of a team,
and wanting to do a good job. “Extrinsic” motivators are those applied to
a person or team, such as arbitrary measurements, capricious decisions,
and threats. Extrinsic motivators drive out intrinsic factors, turning work-
ers into uncaring automatons. This may or may not work in a factory en-
vironment, but is deadly for knowledge workers.
So measurements are an ineffective tool for motivation.
Good measures promote understanding. They transcend the details
and reveal hidden but profound truths. These are the sorts of measures we
should pursue relentlessly.
But we’re all very busy and must be wary of getting diverted by the
measurement process. Successful measures have the following three char-
acteri s ti cs :
They’re easy to do.
Each gives insight into the product andor processes.
The measure supports effective change-making. If we take data
and do nothing with it, we’re wasting our time.

For every measure, think in terms of first collecting the data, then in-
terpreting it to make sense of the raw numbers. Then figure on presenting
the data to yourself, your boss, or your colleagues. Finally, be prepared to
act on the new understanding.

Stop, Look, Listen
In the bad old days of mainframes, computers were enshrined in tech-
nical tabernacles, serviced by a priesthood of specially vetted operators.
Average users never saw much beyond the punch-card readers.
In those days of yore an edit-execute cycle started with punching
perhaps thousands of cards, hauling them to the computer center (being
careful not to drop the card boxes; on more than one occasion I saw grad