Fix #50

This isn't a full fix but I can't seem to reproduce the issue in #50 at
the moment. So for now this just ensures that exceptions in the
constructors get cleaned up properly (so they don't block future
construction attempts against the same pin)

gpiozero/input_devices.py

@@ -63,18 +63,22 @@ class InputDevice(GPIODevice):
         self._inactive_state = GPIO.HIGH if pull_up else GPIO.LOW
         pull = GPIO.PUD_UP if pull_up else GPIO.PUD_DOWN
 
-        # NOTE: catch_warnings isn't thread-safe but hopefully no-one's messing
+        try:
-        # around with GPIO init within background threads...
+            # NOTE: catch_warnings isn't thread-safe but hopefully no-one's
+            # messing around with GPIO init within background threads...
             with warnings.catch_warnings(record=True) as w:
                 GPIO.setup(pin, GPIO.IN, pull)
-        # The only warning we want to squash is a RuntimeWarning that is thrown
+            # The only warning we want to squash is a RuntimeWarning that is
-        # when setting pins 2 or 3. Anything else should be replayed
+            # thrown when setting pins 2 or 3. Anything else should be replayed
             for warning in w:
                 if warning.category != RuntimeWarning or pin not in (2, 3):
                     warnings.showwarning(
                         warning.message, warning.category, warning.filename,
                         warning.lineno, warning.file, warning.line
                     )
+        except:
+            self.close()
+            raise
 
     @property
     def pull_up(self):
@@ -238,6 +242,7 @@ class DigitalInputDevice(WaitableInputDevice):
     """
     def __init__(self, pin=None, pull_up=False, bounce_time=None):
         super(DigitalInputDevice, self).__init__(pin, pull_up)
+        try:
             # Yes, that's really the default bouncetime in RPi.GPIO...
             GPIO.add_event_detect(
                 self.pin, GPIO.BOTH, callback=self._fire_events,
@@ -245,6 +250,9 @@ class DigitalInputDevice(WaitableInputDevice):
             )
             # Call _fire_events once to set initial state of events
             super(DigitalInputDevice, self)._fire_events()
+        except:
+            self.close()
+            raise
 
     def _fire_events(self, channel):
         super(DigitalInputDevice, self)._fire_events()
@@ -287,13 +295,19 @@ class SmoothedInputDevice(WaitableInputDevice):
             queue_len=5, sample_wait=0.0, partial=False):
         self._queue = None
         super(SmoothedInputDevice, self).__init__(pin, pull_up)
+        try:
             self._queue = GPIOQueue(self, queue_len, sample_wait, partial)
             self.threshold = float(threshold)
+        except:
+            self.close()
+            raise
 
     def close(self):
         try:
             self._queue.stop()
         except AttributeError:
+            # If the queue isn't initialized (it's None) ignore the error
+            # because we're trying to close anyway
             if self._queue is not None:
                 raise
         except RuntimeError:
@@ -398,7 +412,11 @@ class MotionSensor(SmoothedInputDevice):
             pin, pull_up=False, threshold=threshold,
             queue_len=queue_len, sample_wait=1 / sample_rate, partial=partial
         )
+        try:
             self._queue.start()
+        except:
+            self.close()
+            raise
 
     motion_detected = _alias('is_active')
 
@@ -425,12 +443,16 @@ class LightSensor(SmoothedInputDevice):
             pin, pull_up=False, threshold=threshold,
             queue_len=queue_len, sample_wait=0.0, partial=partial
         )
+        try:
             self._charge_time_limit = charge_time_limit
             self._charged = Event()
             GPIO.add_event_detect(
                 self.pin, GPIO.RISING, lambda channel: self._charged.set()
             )
             self._queue.start()
+        except:
+            self.close()
+            raise
 
     @property
     def charge_time_limit(self):

gpiozero/output_devices.py

@@ -22,18 +22,22 @@ class OutputDevice(GPIODevice):
     """
     def __init__(self, pin=None):
         super(OutputDevice, self).__init__(pin)
-        # NOTE: catch_warnings isn't thread-safe but hopefully no-one's messing
+        try:
-        # around with GPIO init within background threads...
+            # NOTE: catch_warnings isn't thread-safe but hopefully no-one's
+            # messing around with GPIO init within background threads...
             with warnings.catch_warnings(record=True) as w:
                 GPIO.setup(pin, GPIO.OUT)
-        # The only warning we want to squash is a RuntimeWarning that is thrown
+            # The only warning we want to squash is a RuntimeWarning that is
-        # when setting pins 2 or 3. Anything else should be replayed
+            # thrown when setting pins 2 or 3. Anything else should be replayed
             for warning in w:
                 if warning.category != RuntimeWarning or pin not in (2, 3):
                     warnings.showwarning(
                         warning.message, warning.category, warning.filename,
                         warning.lineno, warning.file, warning.line
                     )
+        except:
+            self.close()
+            raise
 
     def on(self):
         """
@@ -158,12 +162,16 @@ class PWMOutputDevice(DigitalOutputDevice):
     """
     def __init__(self, pin=None):
         super(PWMOutputDevice, self).__init__(pin)
+        try:
             self._frequency = 100
             self._pwm = GPIO.PWM(self._pin, self._frequency)
             self._pwm.start(0)
             self._min_pwm = 0
             self._max_pwm = 1
             self.value = 0
+        except:
+            self.close()
+            raise
 
     def on(self):
         """
@@ -195,13 +203,11 @@ class PWMOutputDevice(DigitalOutputDevice):
     def value(self, n):
         _min = self._min_pwm
         _max = self._max_pwm
-        if _min <= n <= _max:
+        if not _min <= n <= _max:
-            dc = n * 100
+            raise OutputDeviceError(
-        else:
-            raise GPIODeviceError(
                 "Value must be between %s and %s" % (_min, _max)
             )
-        self._pwm.ChangeDutyCycle(dc)
+        self._pwm.ChangeDutyCycle(n * 100)
         self._value = n