retrolefty:
Also not exactly correct. The AVR chip using it's built in design, forces all I/O input pins to input mode upon a reset or power up action. So pins default as input pins and that is not dependent on a users code to set them as such. Only by user programming commands will an I/O pin be switched to output mode. So if you want to wire a series 200 ohm resistor to all I/O pins to protect from possible user software errors or external wiring errors or external hardware component failures, then you are free to do so, but it's not a requirement from the chip's point of view.
OK, I wasn't aware that the I/O pins defaulting to input was physically built-in to the IC, instead I thought the pins were initially defined as inputs automatically as part of the firmware download. Thank you for the information.
In any case, I was refering to accidental shorting between the input signal from the gauge and one of the output wires this type of project will require. Which is possible in the cramped, vibrating, and sometimes thermally extreme environment that exisits behind a car's dashboard. I just didn't do as good of a job explaining it as I should have in my initial reply.