Page 86 - The Art of Designing Embedded Systems

Real Time Means Right Now! 73

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FIGURE 4-7 A performance analyzer‘s output.

stream of photons, pocket-sized, and costing virtually nothing, our elec-
tronic creations give us astonishing new capabilities.
Those of us who spend our working lives parked in front of comput-
ers have even more powerful computational tools. The spreadsheet is a
multidimensional version of the hand calculator, manipulating thousands
of formulas and numbers with a single keystroke. Excel is one of my fa-
vorite engineering tools. It lets me model weird systems without writing a
line of code, and tune the model almost graphically. Computational tools
have evolved to the point where we no longer struggle with numbers; in-
stead, we ask complex “what-if ” questions.
Network computing lets us share data. We pass spreadsheets and
documents among co-workers with reckless abandon. In my experience,
big, widely shared spreadsheets are usually incorrect. Someone injects a
row or column, forgetting to adjust a summation or other formula. The data
at the end is so complex, based on so many intermediate steps, that it’s
hard to see if it’s right or wrong. . . so we assume it’s right. This is the
dark side of a spreadsheet: no other tool can make so many incorrect cal-
culations so fast.
Mechanical engineers now use finite element analysis to predict the
behavior of complex structures under various stresses. The computer mod-
els a spacecraft vibrating as it is boosted to orbit, giving the designers in-
sight into its strength without the need to run expensive tests on shakers.
Yet, finite element analysis is so complex, with millions of interrelated