I'm designing a keyboard. I found some information online about how to make the keyboard be able to detect multiple key presses at the same time (N-key-rollover).
I found this schematic, from this website.
The website says that A and B are the two inputs, and 1 and 2 are the two outputs. I'd select A, then read the values at 1 and 2, and hence know which keys are currently pressed, then do the same with B.
The diodes are to prevent false-positive keypresses. The website explains this in more detail.
What I don't understand, is how 1 or 2 would ever be high? Let's assume A is high, and the bottom left switch is closed, surely its diode is still opposing the current flow, right? How would any current flow to 2?
Is this a matter of conventional vs. electron current flow? Because that always confuses me, but I just can't figure this out.
EDIT, this is active low.