> when you have a microcontroller pin and you configure it as an input, you expect it to SINK current (as in, take voltage 'in'). That's not how it works; inpu

> when you have a microcontroller pin and you configure it as an input, you expect it to SINK current (as in, take voltage 'in'). That's not how it works; input does not mean sink current. An OUTPUT low sinks current, and an output high sources current. In a "normal" microcontroller (with no silicon bugs), an input pin is in a high-impedance state ("Hi-Z"), meaning it doesn't sink or source current -- but it can be configured to have an internal pull-up or pull-down resistor, in which case it will (respectively) source or sink a little bit of current, enough to keep it at high or low voltage (i.e., enough for a logical high or low) unless there's something else driving it. The problem with the RP2350 is that (under some circumstances) there's a current leakage between the pin and the voltage rail, so when a pin is configured as input with a pull-down resistor, the voltage will not go down to the low level it needs to read a logical low as expected: it will be at around 2.2V, which is in the "undefined" region.