BlinkGpioExample.java

// START SNIPPET: blink-gpio-snippet


/*
 * #%L
 * **********************************************************************
 * ORGANIZATION  :  Pi4J
 * PROJECT       :  Pi4J :: Java Examples
 * FILENAME      :  BlinkGpioExample.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 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.RaspiPin;
import com.pi4j.io.gpio.event.GpioPinDigitalStateChangeEvent;
import com.pi4j.io.gpio.event.GpioPinListenerDigital;

/**
 * This example code demonstrates how to perform simple 
 * blinking LED logic of a GPIO pin on the Raspberry Pi
 * using the Pi4J library.  
 * 
 * @author Robert Savage
 */
public class BlinkGpioExample {
    
    public static void main(String[] args) throws InterruptedException {
        
        System.out.println("<--Pi4J--> GPIO Blink Example ... started.");
        
        // create gpio controller
        final GpioController gpio = GpioFactory.getInstance();
        
        // provision gpio pin #01 & #03 as an output pins and blink
        final GpioPinDigitalOutput led1 = gpio.provisionDigitalOutputPin(RaspiPin.GPIO_01);
        final GpioPinDigitalOutput led2 = gpio.provisionDigitalOutputPin(RaspiPin.GPIO_03);

        // 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);

        // create and register gpio pin listener
        myButton.addListener(new GpioPinListenerDigital() {
                @Override
                public void handleGpioPinDigitalStateChangeEvent(GpioPinDigitalStateChangeEvent event) {
                    // when button is pressed, speed up the blink rate on LED #2
                    if(event.getState().isHigh()){
                      led2.blink(200);
                    }                        
                    else{
                      led2.blink(1000);
                    }
                }
            });

        // continuously blink the led every 1/2 second for 15 seconds
        led1.blink(500, 15000);

        // continuously blink the led every 1 second 
        led2.blink(1000);
        
        System.out.println(" ... the LED will continue blinking until the program is terminated.");
        System.out.println(" ... PRESS <CTRL-C> TO STOP THE PROGRAM.");
        
        // keep program running until user aborts (CTRL-C)
        for (;;) {
            Thread.sleep(500);
        }
        
        // stop all GPIO activity/threads
        // (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-gpio-snippet