user10859: I guess I just fried my second DUE in a week. The first I didn't really see what happened, but I couldn't upload any sketches, even if the computer could recognize it, and the SAM would get really hot.
Now, I had it powered by a 12V External supply, through a regulator bringing it down to 9V, and in the exact moment I plugged the USB, with power still on, I got a lot of smoke, smelling of fried electronics :p. Afterwards, I have the same symptoms as I had in the other boards: Green and orange LEDs on, chip very hot, computer recognizing it as a Arduino DUE but not being able to upload any sketches.
What just happened?

user8192: If it was the same sketch involved in the destruction of both it may be a good idea to check to make sure the sketch that is involved as well to make sure there are no logical shorts to ground or other pins. Rugged-Circuits has a list of some common ways the Arduino can get shorted. It is showing the Uno but I am sure all similar rules apply with the exception of total power requirements and other differences between the boards.

10859: <p>I guess I just fried my second DUE in a week. The first I didn't really see what happened, but I couldn't upload any sketches, even if the computer could recognize it, and the SAM would get really hot.</p>

<p>Now, I had it powered by a 12V External supply, through a regulator bringing it down to 9V, and in the exact moment I plugged the USB, with power still on, I got a lot of smoke, smelling of fried electronics :p. Afterwards, I have the same symptoms as I had in the other boards: Green and orange LEDs on, chip very hot, computer recognizing it as a Arduino DUE but not being able to upload any sketches.</p>

<p>What just happened?</p>
 8192: <p>If it was the same sketch involved in the destruction of both it may be a good idea to check to make sure the sketch that is involved as well to make sure there are no logical shorts to ground or other pins. <a href="https://www.rugged-circuits.com/10-ways-to-destroy-an-arduino/" rel="nofollow noreferrer">Rugged-Circuits</a> has a list of some common ways the Arduino can get shorted. It is showing the Uno but I am sure all similar rules apply with the exception of total power requirements and other differences between the boards.</p>
