Page 122 - The Art of Designing Embedded Systems

CHAPTER 6

Hardware Musings

Debuggable Designs

An unhappy reality of our business is that we’ll surely spend lots of
time-far too much time-debugging both hardware and firmware. For
better or worse, debugging consumes project-months with reckless aban-
don. It’s usually a prime cause of schedule collapse, disgruntled team
members, and excess stomach acid.
Yet debugging will never go away. Practicing even the very best de-
sign techniques will never eliminate mistakes. No one is smart enough to
anticipate every nuance and implication of each design decision on even a
simple little 4k 8051 product; when complexity soars to hundreds of thou-
sands of lines of code coupled to complex custom ASICs we can only be
sure that bugs will multiply like rabbits.
We know, then, up front when making basic design decisions that in
weeks or months our grand scheme will go from paper scribbles to hard-
ware and software ready for testing. It behooves us to be quite careful with
those initial choices we make, to be sure that the resulting design isn’t an
undebuggable mess.

Test Points Galore

Always remember that, whether you’re working on hardware or
firmware problems, the oscilloscope is one of the most useful of all de-
bugging tools. A scope gives instant insight into difficult code issues such
as operation of I/O ports, ISR sequencing, and performance problems.

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