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How can I from the shell remove and apply USB power to one of the host USB ports in my machine?

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2 Answers

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This was asked on Stackoverflow and really should have been migrated here.

http://stackoverflow.com/questions/4702216/controlling-a-usb-power-supply-on-off-with-linux

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Funny thing is, that answers is not correct. Echoing suspend to that file will request the device to power off (or suspend), but there will still be 5V on pin 1 in the USB cable, thus the device will still draw power from the USB port. – bjarkef Dec 12 '11 at 6:34
@bjarkef Right - thanks for the heads up. – Paul Dec 12 '11 at 8:34
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So it seems that this cannot be done, which I kind of already suspected.

The advice found in some places about echoing on and suspend to /sys/bus/usb/devices/usb?/power/level does not really remove power from the USB host port, it merely requests the device to go into suspend mode, and vice-versa.

I solved my problem by attaching a USB hub with an external power supply, and then cutting the USB 5V wire in the USB cable going from the host machine to the USB. Then I can turn power on an off from my device via an external power relay connected to the USB hub power supply.

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