Android Studio No USB devices detected

1. First, enable debugger mode in your android device.
2. Go to Device Manager from Start Menu and try to find ADB Interface with an error symbol on it. This generally happens because windows sometimes fail to load all the mobile device drives.
3. Next, Go to http://adbdriver.com/downloads/ and download the driver installer, unzip and run it.
4. Now go to Android Studio and you should find that everything is working fine.

https://stackoverflow.com/questions/37108864/android-studio-2-0-no-usb-devices-detected