I just noticed an interesting behaviour with my Arduino Mega 2560:
When using an external power supply (through the power jack), the USB Auto Reset feature seems to be disabled. So when plugging in a USB cable (with external power on) it doesn't reset automatically but continues running. Is this the intended behaviour? I ask, because for my application this is quite useful, but I need to be sure that the board will always behave this way and that it does not depend on any special configuration I am using.
Can anyone confirm this with any Arduino board? I would especially be interested in any results from the Arduino Uno, because I will later use this board for an important, autonomous application (and would be able to check the debug output before leaving it alone without resetting it).
Thanks! Yours sincerely