Ok, I think this one is clear but want to be sure. I've been working with this Uno (with adaFruit FONA shield) for a few weeks. I plugged it into a 12V ac/dc wall adapter and while it was basically working, when I went to unplug it, it was very hot (regulator I assume).
Oooh, they say, 12V, that shouldn't be a problem they say. Now, when I run the Uno + FONA shield from the FONA's battery it generally works (responds to text messages), but seems to restart often (which I don't remember it doing prior).
Other change is I kept getting "Update your boards and libraries" from the Arduino IDE, so foolishly I did that. Then downgraded that one thing right back to 1.6.20 >:(
When I plug the Uno into the same port using the same cable, it no longer appears in /dev. My Mega2560 does, and takes uploads fine.
Have I fried my Uno? That really ticks me off since 12V is supposed to be "fine." The updates I made to the IDE are irrelevant I assume because the board doesn't appear in /dev.
Thank you-