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- Check for continuity between GND, 3.3 V, 5 V, and 12 V. All of these should be isolated from each other.
- Supply 12 V between GND and 12 V. A current limit of 100 mA should be sufficient for most testing. Switching the relays and/or fans will require more current (up to 4 A). Measure the voltage between GND and 3.3 V, and GND and 12 V.
- Set PB0 high to enable the 5 V converter. Measure the voltage between GND and 5 V.
- Connect an oscilloscope probe between GND and 5 V to measure the ripple noise of the 5 V converter.
- Turn off the power supply.
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