TriggerGpioExample.java

// START SNIPPET: trigger-gpio-snippet


/*
 * #%L
 * **********************************************************************
 * ORGANIZATION  :  Pi4J
 * PROJECT       :  Pi4J :: Java Examples
 * FILENAME      :  TriggerGpioExample.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 - 2013 Pi4J
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */


import java.util.concurrent.Callable;

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.GpioCallbackTrigger;
import com.pi4j.io.gpio.trigger.GpioPulseStateTrigger;
import com.pi4j.io.gpio.trigger.GpioSetStateTrigger;
import com.pi4j.io.gpio.trigger.GpioSyncStateTrigger;

/**
 * This example code demonstrates how to setup simple triggers for GPIO pins on the Raspberry Pi.
 * 
 * @author Robert Savage
 */
public class TriggerGpioExample {
    
    public static void main(String[] args) throws InterruptedException {
        
        System.out.println("<--Pi4J--> GPIO 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 triggers take effect.");
        
        // setup gpio pins #04, #05, #06 as an output pins and make sure they are all LOW at startup
        GpioPinDigitalOutput myLed[] = { 
            gpio.provisionDigitalOutputPin(RaspiPin.GPIO_04, "LED #1", PinState.LOW),
            gpio.provisionDigitalOutputPin(RaspiPin.GPIO_05, "LED #2", PinState.LOW),
            gpio.provisionDigitalOutputPin(RaspiPin.GPIO_06, "LED #3", PinState.LOW) 
          };
        
        // create a gpio control trigger on the input pin ; when the input goes HIGH, also set gpio pin #04 to HIGH
        myButton.addTrigger(new GpioSetStateTrigger(PinState.HIGH, myLed[0], PinState.HIGH));

        // create a gpio control trigger on the input pin ; when the input goes LOW, also set gpio pin #04 to LOW
        myButton.addTrigger(new GpioSetStateTrigger(PinState.LOW, myLed[0], PinState.LOW));

        // create a gpio synchronization trigger on the input pin; when the input changes, also set gpio pin #05 to same state
        myButton.addTrigger(new GpioSyncStateTrigger(myLed[1]));

        // create a gpio pulse trigger on the input pin; when the input goes HIGH, also pulse gpio pin #06 to the HIGH state for 1 second
        myButton.addTrigger(new GpioPulseStateTrigger(PinState.HIGH, myLed[2], 1000));

        // create a gpio callback trigger on gpio pin#4; when #4 changes state, perform a callback
        // invocation on the user defined 'Callable' class instance
        myButton.addTrigger(new GpioCallbackTrigger(new Callable<Void>() {
            public Void call() throws Exception {
                System.out.println(" --> GPIO TRIGGER CALLBACK RECEIVED ");
                return null;
            }
        }));

        // keep program running until user aborts (CTRL-C)
        for (;;) {
            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: trigger-gpio-snippet