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Pi4J Java Examples using the Pi4J Library
There is a newer version: 1.4
// START SNIPPET: blink-trigger-gpio-snippet


/*
 * #%L
 * **********************************************************************
 * ORGANIZATION  :  Pi4J
 * PROJECT       :  Pi4J :: Java Examples
 * FILENAME      :  BlinkTriggerGpioExample.java
 *
 * This file is part of the Pi4J project. More information about
 * this project can be found here:  http://www.pi4j.com/
 * **********************************************************************
 * %%
 * Copyright (C) 2012 - 2016 Pi4J
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Lesser Public License for more details.
 *
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * .
 * #L%
 */

import com.pi4j.io.gpio.GpioController;
import com.pi4j.io.gpio.GpioFactory;
import com.pi4j.io.gpio.GpioPinDigitalInput;
import com.pi4j.io.gpio.GpioPinDigitalOutput;
import com.pi4j.io.gpio.PinPullResistance;
import com.pi4j.io.gpio.PinState;
import com.pi4j.io.gpio.RaspiPin;
import com.pi4j.io.gpio.trigger.GpioBlinkStateTrigger;
import com.pi4j.io.gpio.trigger.GpioBlinkStopStateTrigger;

/**
 * This example code demonstrates how to setup blinking triggers for GPIO pins on the Raspberry Pi.
 *
 * @author Robert Savage
 */
public class BlinkTriggerGpioExample {

    public static void main(String[] args) throws InterruptedException {

        System.out.println("<--Pi4J--> GPIO Blink Trigger Example ... started.");

        // create gpio controller
        final GpioController gpio = GpioFactory.getInstance();

        // provision gpio pin #02 as an input pin with its internal pull down resistor enabled
        final GpioPinDigitalInput myButton = gpio.provisionDigitalInputPin(RaspiPin.GPIO_02,
                                                  PinPullResistance.PULL_DOWN);

        System.out.println(" ... complete the GPIO #02 circuit and see the blink trigger take effect.");

        // setup gpio pins #04 an output pins and make sure they are all LOW at startup
        final GpioPinDigitalOutput myLed = gpio.provisionDigitalOutputPin(RaspiPin.GPIO_04, PinState.LOW);

        // create a gpio control trigger on the input pin ; when the input goes HIGH, turn on blinking
        myButton.addTrigger(new GpioBlinkStateTrigger(PinState.HIGH, myLed, 250));

        // create a gpio control trigger on the input pin ; when the input goes LOW, turn off blinking
        myButton.addTrigger(new GpioBlinkStopStateTrigger(PinState.LOW, myLed));

        // keep program running until user aborts (CTRL-C)
        while(true) {
            Thread.sleep(500);
        }

        // stop all GPIO activity/threads by shutting down the GPIO controller
        // (this method will forcefully shutdown all GPIO monitoring threads and scheduled tasks)
        // gpio.shutdown();   <--- implement this method call if you wish to terminate the Pi4J GPIO controller
    }
}
// END SNIPPET: blink-trigger-gpio-snippet