public class Hardware

Entry point to the buses and pins of the device the application runs on: GPIO lines, I2C, SPI, serial ports, PWM, CAN, the hardware watchdog and the display backlight.

This is the API for boards such as the Raspberry Pi, i.MX, Rockchip and other embedded Linux devices. Every method is available on every platform; a port without the hardware reports it through isSupported(int) and its open methods throw HardwareException, so the same application runs on a phone, a desktop or the simulator.

Hardware hw = Hardware.getInstance();
try {
    if (hw.isSupported(Hardware.FEATURE_GPIO)) {
        final GpioPin led = hw.openGpioOutput("gpiochip0", 17, false);
        led.setHigh(true);

        GpioPin button = hw.openGpioInput("gpiochip0", 27, GpioPin.BIAS_PULL_UP, GpioPin.EDGE_FALLING);
        button.setListener(new GpioListener() {
            public void edgeDetected(GpioPin pin, boolean rising, long timestampNanos) {
                try {
                    led.setHigh(!led.isHigh());
                } catch (HardwareException e) {
                    Log.e(e);
                }
            }
        });
    }
} catch (HardwareException e) {
    Log.e(e);
}

Threading

The transfer methods block for the duration of the bus transaction, which is microseconds for GPIO, I2C and SPI. Serial and CAN reads can wait for data; call them off the event dispatch thread, or use their timeout arguments. Listener callbacks always arrive on the event dispatch thread.

For port implementors

A port subclasses this class and overrides the protected primitives, which take and return integer handles. The device classes (GpioPin, I2cDevice, …) are written once over those primitives, so a port never subclasses them. Every primitive’s default throws HardwareException.