Turn off USB output

[Mars Chak]

Please forgive my limited English. I'm using a USB splitter to connect my phone, power adapter, and USB camera. I want the camera to shut down simultaneously when the power adapter is off, preventing it from drawing power from the phone. My idea is to exploit the phone's USB charging mechanism, which pauses charging when wet. I could use an automate function to trick the phone into thinking it's wet. Is this method feasible?

[мJ Zкxy]

This question is model specific depend on your hardware on some phone it possible to pause charging when battery is 50% for example but I don't know of any flow exist that could trick it.

[Henrik "The Developer" Lindqvist]

Unlikely to be possible, even when using root, since that's a feature handled by the hardware.

[l]

Not directly related to your question, but a warning nevertheless:
Connecting 5 V USB devices (a camera) to a USB hub with certain phones
and power supplies can destroy those USB devices: many power supplies
support Quick Charging methods. With those is the charging voltage set
after negotiation between charger and phone. This may result in
setting to higher voltages than 5 Volt, with the result of damaging the
connected 5 Volt only devices.

[RGeB]

If your device uses a micro-USB OTG port, many Splitter (Y) cables that are set up for simultaneous power and USB data include a diode that does exactly what you want. See the attached fig. If not, assuming the cable has a junction box and you can solder, it is not too hard to add one. By the way the value of R for simultaneous power and data over OTG varies between devices (manufacturers do not heed the USB charging standard).

You could try an Automate Block like enforce Doze. I do not know if that blocks USB power out, and it may vary between devices. 

Sometimes you have to use hardware.

[мJ Zкxy]

Depend on your model quick charging turned off or not until phone get too hot or I think phone could get broken when not charging with fail hardware.