Almost fried on first outing

Hi all - newbie warning! OK, so brand new Uno being played with for the first time, and I almost fried it. All I wanted to do was measure the pd/voltage from my bench power supply using the example code. Supply on 3.5 V, polarity correct, but spurious values and a very hot processor! Quickly disconnected and tried measuring the 5v and 3.3v outputs - no problem. So, is there something silly I have done? I'm running the board on USB power from my laptop with the charger plugged in, and trying to measure a confirmed 3.5V output from a bench power supply. I'm guessing there is an unintended current route I have missed.

Thanks for any ideas.

What part did you apply the bench supply to? Check it with an AVO. If the processor got hot theres no point in checking the output from the voltage reg!.

Can you still run the blink example? If not you fried the processor.

Does the pin you applied the bench supply to still work?


Which example code?


As above, hard to say without knowing more about what you have connected up.