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package com.diozero.api;
/*
* #%L
* Organisation: diozero
* Project: diozero - Core
* Filename: DebouncedDigitalInputDevice.java
*
* This file is part of the diozero project. More information about this project
* can be found at https://www.diozero.com/.
* %%
* Copyright (C) 2016 - 2021 diozero
* %%
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
* #L%
*/
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import org.tinylog.Logger;
import com.diozero.util.DiozeroScheduler;
import com.diozero.util.SleepUtil;
/**
* Digital input device with debounce logic. The goal of this debounce
* implementation is to only detect level changes that are held for the
* specified debounce time. All other level changes that are shorter than that
* duration will be ignored.
*/
public class DebouncedDigitalInputDevice extends DigitalInputDevice {
private int debounceTimeMs;
private Queue eventQueue;
private Future changeDetectionFuture;
private AtomicBoolean running;
private boolean lastReportedValue;
private boolean nextValue;
private long changeTimeMs;
private long changeTimeNs;
/**
* @param gpio GPIO
* @param debounceTimeMs Specifies the length of time (in seconds) that the
* component will ignore changes in state after an initial
* change.
* @throws RuntimeIOException if an I/O error occurs
* @throws IllegalArgumentException if the debounce time is less than 0
*/
public DebouncedDigitalInputDevice(int gpio, int debounceTimeMs)
throws RuntimeIOException, IllegalArgumentException {
this(gpio, GpioPullUpDown.NONE, GpioEventTrigger.BOTH, debounceTimeMs);
}
/**
* @param gpio GPIO
* @param pud Pull-up/down configuration
* @param debounceTimeMs Specifies the length of time (in seconds) that the
* component will ignore changes in state after an initial
* change.
* @throws RuntimeIOException if an I/O error occurs
* @throws IllegalArgumentException if the debounce time is less than 0
*/
public DebouncedDigitalInputDevice(int gpio, GpioPullUpDown pud, int debounceTimeMs)
throws RuntimeIOException, IllegalArgumentException {
this(gpio, pud, GpioEventTrigger.BOTH, debounceTimeMs);
}
private DebouncedDigitalInputDevice(int gpio, GpioPullUpDown pud, GpioEventTrigger trigger, int debounceTimeMs)
throws RuntimeIOException, IllegalArgumentException {
super(gpio, pud, trigger);
if (debounceTimeMs <= 0) {
throw new IllegalArgumentException("Debounce time must be > 0");
}
this.debounceTimeMs = debounceTimeMs;
// Initialise nextValue and lastReportedValue to the current value
nextValue = lastReportedValue = getValue();
changeTimeMs = System.currentTimeMillis();
changeTimeNs = System.nanoTime();
eventQueue = new ConcurrentLinkedQueue<>();
running = new AtomicBoolean(true);
changeDetectionFuture = DiozeroScheduler.getNonDaemonInstance().submit(this::changeDetection);
}
@Override
public void accept(DigitalInputEvent event) {
eventQueue.add(event);
}
@Override
public void close() {
Logger.trace("close()");
if (running.getAndSet(false)) {
changeDetectionFuture.cancel(true);
try {
changeDetectionFuture.get(1, TimeUnit.MILLISECONDS);
} catch (Exception e) {
// Ignore
}
}
super.close();
}
/*-
* +--------------+ +--------------+ +--------------+ +------
* | | | | | | |
* --------------+ +--------------+ +--------------+ +--------------+
* |---------|---------|---------|---------|---------|---------|---------|---------|---------|---------|---------|
* t=0 t=10 t=20 t=30 t=40 t=50 t=60 t=70 t=80 t=90 t=100
* eT=0 eT=0 eT=14 eT=29
* eV=0 eV= eV=1 eV=0
* nV=0 nV=0 nV=1 nV=1
* lV=0 lV=0 lV=0 lV=0
*/
public void changeDetection() {
long start_ms;
while (running.get()) {
start_ms = System.currentTimeMillis();
// Process all events in eventQueue
// No need to synchronise as we're using a ConcurrentLinkedQueue
// Process all events on the queue
DigitalInputEvent event = eventQueue.poll();
while (event != null) {
// Check if the previous event was held for debounceTimeMs.
// This can happen if an event occurred mid-sleep hence isn't caught by the
// check at the end of the event processing loop.
if (nextValue != lastReportedValue && (event.getEpochTime() - changeTimeMs) >= debounceTimeMs) {
super.accept(new DigitalInputEvent(getGpio(), changeTimeMs, changeTimeNs, nextValue));
lastReportedValue = nextValue;
changeTimeMs = event.getEpochTime();
}
boolean value = event.getValue();
// Record the time of change if there is a difference between event value and
// the next value to be reported.
// Note that you sometimes get repeat events for the same value.
if (value != nextValue) {
changeTimeMs = event.getEpochTime();
changeTimeNs = event.getNanoTime();
nextValue = value;
}
// Get the next event (if there is one)
event = eventQueue.poll();
}
// Only fire an event when there has been a change to the last reported value
// that has been held for at least debounceTimeMs
if (nextValue != lastReportedValue) {
// Note that an event might have arrived during the sleep period
long diff_ms = System.currentTimeMillis() - changeTimeMs;
/*-
Logger.debug("nextValue ({}) != lastReportedValue ({}), diff_ms: {}, debounceTimeMs: {}",
Boolean.valueOf(nextValue), Boolean.valueOf(lastReportedValue), Long.valueOf(diff_ms),
Long.valueOf(debounceTimeMs));
*/
if (diff_ms >= debounceTimeMs) {
// FIXME This calls out to user code in the same thread hence can delay start of
// the next loop
super.accept(new DigitalInputEvent(getGpio(), changeTimeMs, changeTimeNs, nextValue));
lastReportedValue = nextValue;
// Reset the changeTimeMs value so we don't send this event again
changeTimeMs = System.currentTimeMillis();
changeTimeNs = System.nanoTime();
}
}
// Sleep for debounceTimeMs - the time taken to process events
long sleep_ms = debounceTimeMs - (System.currentTimeMillis() - start_ms);
if (sleep_ms > 0) {
SleepUtil.sleepMillis(sleep_ms);
} else if (Logger.isDebugEnabled()) {
Logger.debug("Not sleeping - sleep_ms: {}", Long.valueOf(sleep_ms));
}
}
Logger.debug("Exiting run loop");
}
}
