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// START SNIPPET: frequency-gpio-snippet


/*
 * #%L
 * **********************************************************************
 * ORGANIZATION  :  Pi4J
 * PROJECT       :  Pi4J :: Java Examples
 * FILENAME      :  FrequencyGpioExample.java
 *
 * This file is part of the Pi4J project. More information about
 * this project can be found here:  https://pi4j.com/
 * **********************************************************************
 * %%
 * Copyright (C) 2012 - 2021 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.GpioPinDigitalOutput;
import com.pi4j.io.gpio.PinState;
import com.pi4j.io.gpio.RaspiPin;

/**
 * This example code provides a continuous GPIO pin state
 * changes on the Raspberry Pi to allow measurement of
 * frequency.
 *
 * @author Robert Savage
 */
public class FrequencyGpioExample {

    public static void main(String[] args) {

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

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

        // provision gpio pin #01 as an output pin and turn on
        final GpioPinDigitalOutput pin = gpio.provisionDigitalOutputPin(RaspiPin.GPIO_01, PinState.LOW);

        // continuous loop
        while(true) {
            pin.setState(true);
            pin.setState(false);
        }

        // 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: frequency-gpio-snippet