6: It Doesn’t Work!

CET360Microprocessor Engineering

J. Sumey

2

Stuck in the mud…

“I’ve built and programmed my prototype, but it doesn’t work!”

Now What???

3

Wrong Reactions

throw things and curse stomp around awhile and leave haphazardly change wires start taking pot shots at the

software wait for instructor to fix it

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Right Reactions

apply a logical methodology to identifying and correcting the problem

backtrack: when did it last work? what changes were made since then? consult journal!

5

Divide and Conquer!

is the problem: hardware? software? or both!?

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Hardware Problems breadboard / wiring errors power supply errors dead batteries shorts faulty components

always be aware! look – smell – touch

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Hardware Troubleshooting

schematic power supply ammeter oscilloscope DSO / logic analyzer LEDs datasheets

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Software Problems

semantic/logic errors data representation errors operator mis-precedence side effects ISR issues I/O register configuration errors

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Software Troubleshooting

breakpoints/single-stepping register/memory display &

manipulation software triggers linker map “heartbeat” debug pulses back-ups!

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Other Tips

SEE (Someone Else’s Eyes) document everything (lab journal) re-read datasheets design reviews