USB hub as to connect some extra device
Any powered hub that has no switches or isolation and feeds 5V upstream is usually not compliant to the USB standard. For OTG ports it can be different since there are special power switches to implement protection. Feeding the 5V from the hub back into the host can lead to all sorts of damage because any difference in the 5V of the two power supplies will cause a rather large current to flow and probably damage one of the regulators and if the Pine is not powered you can cause a latch-up in the I/O pins of the processors if there are no series protection resistors. You can try to what you proposed and cut the 5V in the upstream port, but there might be still difference in the signal levels if the 5V of the hub differ to far from the 5V of the Pine.
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RE: USB hub as to connect some extra device - by xalius - 06-28-2016, 06:30 AM

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