2 suggestions for hardware robustness

[evanshultz]

Great work! Thanks for sharing.

There are two hardware suggestions I have which aren't too important for a hobby project but are good practice. They cover unlikely scenarios, but are worthwhile for robustness.

First, I suggest adding a reverse diode across the regulator, with the anode at the regulator output. If the input voltage drops below the output voltage, which can sometimes happen during power off, the pass transistor in the regulator can become damaged by reverse current. This is probably unlikely since the power supply output likely has a very long holdup, but it won't hurt and there could be conditions that would cause the regulator input voltage to fall first. A standard 4148 will suffice.

Second, depending on what receives the signal in the laptop, it may also be prudent to put Schottky diodes from ground to the uC signal output and from the uC output to +3.3V. A series resistor between the uC and diodes is also good protection. The receiving circuitry could pull the pin below ground or above +3.3V in an unexpected condition, generally a serious fault, which would likely damage the uC.