General Purpose Input/Output (GPIO) Interface Overview and Usage Steps on Raspberry Pi

General Purpose Input/Output (GPIO) provides a programmable interface for reading binary input devices (e.g., switches) and controlling binary output devices (e.g., LEDs) on a Raspberry Pi.

1. Open Connection – Create a PeripheralManagerService object and call openGpio() with the desired port name.

2. Read Input – Set the pin direction to DIRECTION_IN , configure active type with ACTIVE_HIGH or ACTIVE_LOW , then call getValue() to obtain the current state.

3. Monitor Input Changes – Register a GpioCallback , set edge trigger type ( EDGE_NONE , EDGE_RISING , EDGE_FALLING , or EDGE_BOTH ), and handle events in onGpioEdge() . Unregister handlers when not needed.

4. Write Output – Set direction to DIRECTION_OUT_INITIALLY_HIGH or DIRECTION_OUT_INITIALLY_LOW , configure active type, and use setValue() to control the pin state.

5. Close Connection – Call close() on the GPIO object to release resources.

Case Demonstration

Hardware: Raspberry Pi board, breadboard, LED, switch, resistors, and jumper wires.

Circuit diagram:

Code location: GpioDemo\app\src\main\java\com\chengxiang\gpiodemo\MainActivity.java

Running result: Toggling the button switches the LED on and off.

Tip 1 – Using BCM6 may cause errors; switching to BCM5 resolves the issue, possibly due to a bug in the Things system.