Good point, I hadn't thought of that for this use! An input has a high impedance, which is to say a very large (giga-ohm) resistance to vcc/gnd: very little cu

Good point, I hadn't thought of that for this use! An input has a high impedance, which is to say a very large (giga-ohm) resistance to vcc/gnd: very little current will flow trough. Usually it's connected to the gate of a transistor, which can easily be damaged by high voltages (3V instead of 1.2 can be enough). You can achieve the same effect, but more resilient to high voltages, by switching the output pin to an open drain/open collector mode, which disable the pull-up (pmos) transistor. That gives you high impedance when the pull-down transistor is enabled (ie, 1 is written to the output). This can also be used to control high-voltage logic/LEDs with a low-voltage microcontroller. https://en.wikipedia.org/wiki/Open_collector https://en.wikipedia.org/wiki/Open_collector https://blog.stratifylabs.co/device/2013-10-21-Understanding-Microcontroller-Pin-Input-Output-Modes/ https://blog.stratifylabs.co/device/2013-10-21-Understanding...