- How random would an analog read on a spare pin on the Nano actually be? I'd imagine it probably settles around a certain range and stays there.
That's true and you can test that to see how much "noise" you are getting...
If you add an "antenna" (a "long" unshielded wire) to the analog input you can pick-up electro-magnetic radiation from the 50/60Hz power lines all-around you. (Or if you have a built-in power supply you may be able to get an AC voltage from the transformer-output.) That's not truly-random but it's variable and it's uncorrelated with the start-up time of the processor. Or, you can build an analog random noise generator. Somewhere I read that something like that is used in casinos.
It usually comes-down to, "How random" does it need to be?" In most applications you just need "unpredictable" or hard-to-predict results and usually you CAN get "random enough".
...You can get into crazy-philosophical discussions about, "Does true-randomness exist?" With enough knowledge could someone (or some machine) predict the results? Can God predict the results? But I just ask, "Is it random enough?" or "Is it unpredictable enough?"
I know what you're thinking, and no unfortunately there isn't
I have no inputs at all. I'm open to adding something
If it's THAT important you can add a button for "human randomness timing". (i.e. FORCE a button-press by holding-up everything in a loop until the button is pushed to seed the random number generator, etc.)