Android USB OTG: programmatically turn off power to the port

24
votes

Suppose I have a USB-powered LED lamp connected through a USB OTG adapter to a Toshiba Excite 10 tablet running Android 4.0.3, which provides the power.

I want to programmatically turn the USB OTG host port's power pins on and off from an app. (Ideally without root, but I'll take what I can get). Any ideas?

2
androidusbusb-otg
Not sure if my kernel is compatible but it looks like I might just need to write to the file /sys/bus/usb/devices/usb3/power/level. I tried this without root but the write fails, so next I guess I need to root my tablet and try again. Source: stackoverflow.com/questions/4702216/… – AlcubierreDrive

2 Answers

4
votes

You must have write permission on /sys directory. Rooting makes the process very easy. Just root your device and issue the right echo command to toggle kernel status bits like : 

String[] command = { "/system/bin/sh", "-c", "echo xxx > /sys/bus/usb/devices/usb3/power/level", };
Runtime.getRuntime().exec(command);

Another way is to use libusb, dig the library for the function that cuts the power off. You can use android.hardware.usb.UsbManager to request proper permission for libusb.

1
votes

As I know from here https://askubuntu.com/questions/342061/power-on-off-usb-ports "All of the previous answers talk about a USB suspend mechanism, i.e. a "logical power-off", they will never physically cut the VBUS +5V from the USB port.".

Maybe a hardware solution is bad idea, but I can advise you to use MOSFET transistor with programmed Atmega8U4 chip on PCB, that is programmed to cutoff power to led lamp.