Qsilverrdc:
I was reading the Cpu doc's :~ (Not sure if that's a good thing)The Atmel328 document says that If the I/O pin is configured as input and internally pulled up, it will source current if externally pulled low.
So what I have drawn in schematic is a short, when I close the switch?
If that's true, is there another way to do the circuit without adding a load resistor, or external pull ups?
Just looking for measurable input signals.
Rich
Not if you are trying to 'read' a simple switch contact. An input pin must be presented with at all times with either a valid digital HIGH voltage or LOW voltage. A 'dry' switch contact is not capable of supplying either as it just offers a 0 ohm connection when closed and a open circuit when opened between it's two contact pins. See the difference? The input pin is designed to sense the voltage level wired to it's input, so it's up to you to provide the proper wiring and components to preset both the valid high and low voltage levels.
Lefty