HiI have an Arduino Mega 2560. The description states that the power source is selected automatically.I would like to know how this is done. If the Mega is connected to a powered USB port (5V) and a 9V battery block on VIN, which is it going to use?If both external power and USB power are avalible, the auto-voltage selection feature will select the external power.If it uses the USB supply as first choice this setup would make an easy battery backed system.If not would the reverse work, have a regulated battery on the USB port an the VIN connected to mains.Yes, it works 'backwards' so supplying regulated +5vdc from a battery supply wired to the +5vdc and ground power pins of the USB connector or the +5vdc and ground shield connector pins would allow the external power connector to be normal mains power with automatic switching to the USB or +5vdc pin supplied power.Cheers
How do I disable the Mega2560 from powering up via USB? I am supplying external power VIN and only want to use that, as the current drain is too high for USB. The voltages are too low when USB is connected.