USB-Controller is a free Android app developed by teraKUHN that transforms your smartphone into a microcontroller. It allows you to control hobby lights or motors through your device's USB-OTG port. With this app, you can set or clear up to eight signals (Data D0 through D7) without the need for a separate Arduino controller.

To use the app, you need to create a harness that connects your Android device with USB-OTG hardware support to an IEEE-1284 parallel printer port. After that, you can build your own light or motor interface to the parallel ports binary outputs. The app also helps you determine if your Android device has USB-OTG hardware support by recognizing a USB device plugged into your device.