I needed more digital pins for a project. The answer for me was register chips and all is good.
But while trying to come up with a solution, one of the ideas I discarded was using a second arduino. And this brought up a question that's been bugging me. Is there any way that two arduinos could share a digital input? For instance if I have a button and I set two pins to INPUT_PULLUP, one on each arduino. I have ground and power going into arduino 1. I imagine taking that power and putting it into the input of arduino 2 would be bad, right? Is there any configuration that would allow me to do this?
No practical use for this really, but just something making me really curious.