Page 183 - The Art of Designing Embedded Systems

170 THE ART OF DESIGNING EMBEDDED SYSTEMS

solder drippings and wire segments off the bench once in a while and your
incidence of catastrophic failures will plunge dramatically.
An organized lab promotes correctness. How many times have you
seen engineering changes that never quite made it into production because
someone forgot to write them down? Or because the notation was made on
the comer of a napkin that was accidentally used to wipe up a spill and then
thrown away?
When starting to debug a new project, remove everything from the
bench and sweep it clean. A quick wipe with a damp cloth removes those
accumulated coffee stains. Then, put everything not absolutely needed
back on the shelves. This is the unique chance we get once in a while to re-
move the clutter, so be relentless.
Any embedded project will require at least a computer and a scope.
Decide what test equipment you’ll use continuously, and which will be
used only on an as-needed basis. All too often even a simple embedded sys-
tem has some sort of communications link requiring an extra computer as a
source of data. I like to use a laptop for this as it requires little bench space.
Be sure you can easily reach the computer’s frequently used connec-
tors. If two different devices must share an RS-232 port, buy a switch box
and reduce the wear and tear on connectors . . . and your back.
Don’t work with unacceptable power distributions. Too many of us
spend half our lives swapping power plugs. Buy outlet strips or wire up a
decent source of AC mains to your test bench.
Miles and Beryl Smeaton sailed their aging boat around Cape Horn
many years ago with expert boatbuilder John Guzzwell as crew. When the
boat flipped in 30-foot seas and the hull cracked open, Guzzwell was
shocked to discover that all of the Smeaton’s tools were rusty and dull. As
water poured in he carefully sharpened and cleaned the tools before un-
dertaking the repairs that eventually saved their lives.
The moral is to buy good tools and take care of them. You’ll live with
those dikes and needle-nose pliers for weeks on end. Buy cheap stuff and
your blood pressure will skyrocket every time you can’t clip a lead close
to the board. Keep them organized-get a little toolbox to keep them from
falling onto the floor and getting lost.
How is your soldering equipment? A vacuum desolderer is great for
making large-scale changes, but during prototyping I find it’s often easier
just to hack away at the board, mounting chips on top of chips and using
plenty of blue wire.
During the first few days (or weeks) of bringing up a new embedded
system I often find myself making lots of little modifications to the system.
A hot iron always at hand is critical. After things start to more or less