HCSR501.java

/*
Copyright 2016-2017 Paul Trebilcox-Ruiz

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.
*/

package com.awkwardelk.hardware;

import com.google.android.things.pio.Gpio;
import com.google.android.things.pio.GpioCallback;
import com.google.android.things.pio.PeripheralManagerService;

import java.io.IOException;

@SuppressWarnings({"unused", "WeakerAccess"})
public class HCSR501 implements AutoCloseable {

    public enum State {
        STATE_HIGH,
        STATE_LOW;
    }

    public interface OnMotionDetectedEventListener {
        void onMotionDetectedEvent(State state);
    }

    private Gpio mMotionDetectorGpio;
    private OnMotionDetectedEventListener mOnMotionDetectedEventListener;

    private boolean mLastState;

    public HCSR501(String pin) throws IOException {
        PeripheralManagerService pioService = new PeripheralManagerService();

        Gpio HCSR501Gpio = pioService.openGpio(pin);

        try {
            connect(HCSR501Gpio);
        } catch( IOException | RuntimeException e ) {
            close();
            throw e;
        }
    }

    private void connect(Gpio HCSR501Gpio) throws IOException {
        mMotionDetectorGpio = HCSR501Gpio;
        mMotionDetectorGpio.setDirection(Gpio.DIRECTION_IN);
        mMotionDetectorGpio.setEdgeTriggerType(Gpio.EDGE_BOTH);

        mLastState = mMotionDetectorGpio.getValue();

        mMotionDetectorGpio.setActiveType(mLastState ? Gpio.ACTIVE_HIGH : Gpio.ACTIVE_LOW);

        mMotionDetectorGpio.registerGpioCallback(mInterruptCallback);
    }

    private void performMotionEvent(State state) {
        if( mOnMotionDetectedEventListener != null ) {
            mOnMotionDetectedEventListener.onMotionDetectedEvent(state);
        }
    }

    private GpioCallback mInterruptCallback = new GpioCallback() {

        @Override
        public boolean onGpioEdge(Gpio gpio) {
            try {

                if( gpio.getValue() != mLastState ) {
                    mLastState = gpio.getValue();
                    performMotionEvent(mLastState ? State.STATE_HIGH : State.STATE_LOW);
                }


            } catch( IOException e ) {

            }

            return true;
        }
    };

    public void setOnMotionDetectedEventListener(OnMotionDetectedEventListener listener) {
        mOnMotionDetectedEventListener = listener;
    }

    @Override
    public void close() throws IOException {
        mOnMotionDetectedEventListener = null;

        if (mMotionDetectorGpio != null) {
            mMotionDetectorGpio.unregisterGpioCallback(mInterruptCallback);
            try {
                mMotionDetectorGpio.close();
            } finally {
                mMotionDetectorGpio = null;
            }
        }
    }

}

Not using the UserSensor framework. Will need to be reworked to support proper driver usage. Good enough for simple use, however.