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I have an Arduino Due. It communicate to the computer with the native usb port. It is also powered by the native port. Anyway, the connected sensors are pretty sensitive to the current, thus I would like to use a power supply (as a portable smartphone charger) in order to provide the current at the Arduino.

How can I say to the Arduino to get the current from another 'port' (e.g. the serial programming) and use the native port only for the communications?

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You can't really fiddle with the power circuitry of the Due. If external sensors need more power than the due can provide through its internal 5V connection, whatever you choose that to be (dictated by the USB connection used) then you will either have to use a higher voltage to feed the barrel jack, or better, power the sensors separately to the Due. Just remember to connect the grounds.

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  • beside, the USB power selector on the Arduino 2 is pretty crappy. The serial programming port has a pMOSFET connected as an "ideal diode" (gate grounded, drain toward the power). The other port has a similar connection, except that the gate is driven by a comparator circuit. However if Vin=0, the comparator outputs 0, and drives the gate low. The problem is that a mosfet connected as an "ideal diode", once it's on, it also conducts backwards, as long as VGS > VTH. Therefore current can flow between the VDD of two USB ports... Yes, the same can occur with external VIn and the serial USB. – next-hack Aug 25 '17 at 6:24

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