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Edited by Werner at 2018-5-5 18:35
From the paper provided here http://linux-sunxi.org/images/7/ ... Schematics_v2.0.pdf
I can read that the dc input is directly connected to the USB 5V through a low ohm resistor.
I do not have the proper tools to test this, for example through a potentiometer. Anyway, I connected my smartphone to the usb Port and measured the current flowing into the phone. Without the load I had pretty accurate 5V at the USB port. When connected the Voltage dropped to about 4.8V with a current draw of 0.44amps.
As second test I used an external dvd writer. I could not mount a disc into file systems, probably due to missing support in the provided kernel, so I could not get it to spin properly. Anyway. During insertion and drive internal reading of the disc I could pull a current close to 0.9 amp from the USB port. The voltage dropped to a bit under 4.8v. This however might be related to the power supply which should be able to provide 2.4amps though.
As a last test I utilized an external USB hard disk. Single USB3 connector, designed for 2,5'' hard drives, no external power supply. Ran flawless and drained about half an amp.
All those tests have been done using the micro USB OTG port and not the standard USB port.
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