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I've been wondering about buying an LG 23ET63V touch screen monitor.
Although the manual doesn't mention the touchscreen usb output specifications, I was wondering if anyone knows whether this could be sufficient to both power a Raspberry Pi 2 and output the touch signals?

The point would be to try and eliminate the Raspberry's power adapter altogether.

Wim Ombelets
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    Powering an upstream device is a violation of USB specifications. –  Feb 29 '16 at 07:20
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    Agreed. You'll probably get in a loop when the monitor goes to sleep due to no activity from the Pi, shuts off the Pi and, well, that's all. – Transistor Feb 29 '16 at 07:24
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    Raspberry Pi can accept power through the type A sockets, but I doubt that the monitor provides power through the type B socket used to access the touchscreen. if the monitor has an in-built USB hub that could perhaps be used to power the Raspberry Pi – Jasen Feb 29 '16 at 09:35

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The USB socket on your monitor is designed to accept USB B plug:

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This type of plugs is only used on slave devices, and it's almost certainly protected from back-feeding any electrical power back to the USB master. It's very unlikely you will get any current out of it. Depending on the design, it may even require the RPi to provide some electrical power for the touch screen to function.

Dmitry Grigoryev
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    While this is correct, I already encountered touchscreen monitors which had an USB-A socket and an USB-A<->USB-A cable in the box. Made in China. Sigh. – Janka Oct 24 '16 at 15:46
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USB outputs are typically limited to 500 mA, whereas the Raspberry Pi, especially version 2 and 3, need more than that.

tlhIngan
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  • limited per specification, sure, real life not so much. Most hubs (which one would expect to be integrated in said display) usually do not care much for this part of the spec. – Ghanima Dec 27 '17 at 17:26
  • Ports that are designated as "charging ports" will exceed the spec. – tlhIngan Dec 27 '17 at 19:08