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Arduino: Don’t forget…

Don’t forget that the MCU on Netduino and some Arduino boards are powered by 3V3, which means also the inputs and outputs are adapted to 3V3. They generally support up to 5V on digital inputs, but you will get messed up analog values if you make a mistake here, and 3V3 output might not be enough for connected components, etc.

Also, I generally recommend a protecting resistor on otherwise potentially short-circuited pins. Think e.g. a DIP switch without resistors, and one or more of the pins mistakenly set to outputs (due to a bug or by installing the wrong firmware). Based on a true story.

In any case, all pins are set as digital (and very high-resistive) inputs when the MCU is powered on, to avoid toasting the MCU by default.