PCB problems that look like firmware bugs

6 PCB layout failures that firmware engineers think are their bugs.

1. 3.3V rail dropping to 2.1V under load - firmware looks like a race condition, it's actually power delivery
2. Reset trace routed next to switching regulator - sporadic resets that disappear when you probe them
3. Crystal too far from MCU pins - timing drift that shows up only after temperature soak
4. Decoupling capacitor placement omitted - intermittent register reads that look like volatile misuse
5. Ground plane split under ADC - noisy readings that firmware can't filter out
6. USB connector ESD path missing - device enumeration failures that happen only on cold mornings

Every embedded engineer who has shipped product has chased at least three of these. The ones who blamed firmware first spent weeks finding hardware problems later.

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