Controlling motor or lamps is easy, just change the state of a bit and the output changes accordingly. I made a simple cable adapter to use 9V devices so I can use more recent motors, even Power Functions 1.0 motors and LED’s. The PF Medium Motor works fine, just a bit more slow because maximum voltage is around 4.5V instead of 9V.
Read sensors is not so simple. When idle they are always high. When I shorted them the green LED blinks very quickly and then returns to high again.
I have an optosensor and it changes when passing a yellow brick at front (according to the user guides, the optosensor seems to react better to yellow) and it also changes when passing my hand between it and a light source or when pointing a ligth source directly to it. But it doesn’t “keep” that state, after a second or two it returns to high.
So I thing the sensor inputs react only to change, perhaps through a capacitor.
Using the same cable adapter I can use the RCX touch sensors with the Interface A
It works but it seems to only detect releases, not presses.
So for the inputs to be usefull we might have to take in account more than just the current state. And perhaps a counter also helps.