Implemented debouncing of interrupts (Github Issue 5)

README.md

@@ -55,13 +55,13 @@ $pin->setEdge(InputPinInterface::EDGE_BOTH);
 // Create an interrupt watcher
 $interruptWatcher = $gpio->createWatcher();
 
-// Register a callback to be triggered on pin interrupts
+// Register a callback to be triggered on pin interrupts with a 500 millisecond debounce delay
 $interruptWatcher->register($pin, function (InputPinInterface $pin, $value) {
     echo 'Pin ' . $pin->getNumber() . ' changed to: ' . $value . PHP_EOL;
 
     // Returning false will make the watcher return false immediately
     return true;
-});
+}, 500);
 
 // Watch for interrupts, timeout after 5000ms (5 seconds)
 while ($interruptWatcher->watch(5000));

src/Interrupt/InterruptWatcher.php

@@ -12,6 +12,8 @@ class InterruptWatcher implements InterruptWatcherInterface
     private $streams;
     private $pins;
     private $callbacks;
+    private $delays;
+    private $lastCallbacks;
 
     /**
      * Constructor.
@@ -40,7 +42,7 @@ public function __destruct()
     /**
      * {@inheritdoc}
      */
-    public function register(InputPinInterface $pin, callable $callback)
+    public function register(InputPinInterface $pin, callable $callback, int $delay = 0)
     {
         $pinNumber = $pin->getNumber();
 
@@ -54,6 +56,8 @@ public function register(InputPinInterface $pin, callable $callback)
 
         $this->pins[$pinNumber] = $pin;
         $this->callbacks[$pinNumber] = $callback;
+        $this->debounceDelays[$pinNumber] = (float)$delay / 1000;
+        $this->lastCallbackMicrotimes[$pinNumber] = 0;
     }
 
     /**
@@ -68,6 +72,7 @@ public function unregister(InputPinInterface $pin)
 
             unset($this->streams[$pinNumber]);
             unset($this->callbacks[$pinNumber]);
+            unset($this->debounceDelays[$pinNumber]);
             unset($this->pins[$pinNumber]);
         }
     }
@@ -81,6 +86,8 @@ public function watch($timeout)
         $carry = $timeout - ($seconds * 1000);
         $micro = $carry * 1000;
 
+        $microtimeNow = microtime(true);
+
         $read = $write = [];
         $except = $this->streams;
 
@@ -103,6 +110,16 @@ public function watch($timeout)
         }
 
         foreach ($triggers as $pinNumber => $value) {
+            if ($this->debounceDelays[$pinNumber] !== 0
+                && $this->lastCallbackMicrotimes[$pinNumber] !== 0 
+                && ($microtimeNow - $this->lastCallbackMicrotimes[$pinNumber] < $this->debounceDelays[$pinNumber])
+            ) {
+
+                return true;
+            }
+
+            $this->lastCallbackMicrotimes[$pinNumber] = $microtimeNow;
+
             if (false === call_user_func($this->callbacks[$pinNumber], $this->pins[$pinNumber], $value)) {
                 return false;
             }

src/Interrupt/InterruptWatcherInterface.php

@@ -11,8 +11,9 @@ interface InterruptWatcherInterface
      *
      * @param InputPinInterface $pin
      * @param callable $callback
+     * @param integer $delay time in ms between callbacks
      */
-    public function register(InputPinInterface $pin, callable $callback);
+    public function register(InputPinInterface $pin, callable $callback, int $delay = 0);
 
     /**
      * Unregister a pin callback.