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Merge pull request #418 from waveform80/fix-distance-sensor

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Patch for #385
This commit is contained in:
Dave Jones
2016-08-30 23:38:25 +01:00
committed by GitHub
parent 6b7e49f0b3 ab61fa9b6d
commit 15b6ea25b0
1 changed files with 13 additions and 4 deletions
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17
gpiozero/input_devices.py
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@@ -585,11 +585,19 @@ class DistanceSensor(SmoothedInputDevice):
self._max_distance = max_distance self._max_distance = max_distance
self._trigger = GPIODevice(trigger) self._trigger = GPIODevice(trigger)
self._echo = Event() self._echo = Event()
self._echo_rise = None
self._echo_fall = None
self._trigger.pin.function = 'output' self._trigger.pin.function = 'output'
self._trigger.pin.state = False self._trigger.pin.state = False
self.pin.edges = 'both' self.pin.edges = 'both'
self.pin.bounce = None self.pin.bounce = None
self.pin.when_changed = self._echo.set def callback():
if self._echo_rise is None:
self._echo_rise = time()
else:
self._echo_fall = time()
self._echo.set()
self.pin.when_changed = callback
self._queue.start() self._queue.start()
except: except:
self.close() self.close()
@@ -672,14 +680,15 @@ class DistanceSensor(SmoothedInputDevice):
self._trigger.pin.state = False self._trigger.pin.state = False
# Wait up to 1 second for the echo pin to rise # Wait up to 1 second for the echo pin to rise
if self._echo.wait(1): if self._echo.wait(1):
start = time()
self._echo.clear() self._echo.clear()
# Wait up to 40ms for the echo pin to fall (35ms is maximum pulse # Wait up to 40ms for the echo pin to fall (35ms is maximum pulse
# time so any longer means something's gone wrong). Calculate # time so any longer means something's gone wrong). Calculate
# distance as time for echo multiplied by speed of sound divided by # distance as time for echo multiplied by speed of sound divided by
# two to compensate for travel to and from the reflector # two to compensate for travel to and from the reflector
if self._echo.wait(0.04): if self._echo.wait(0.04) and self._echo_fall is not None and self._echo_rise is not None:
distance = (time() - start) * self.speed_of_sound / 2.0 distance = (self._echo_fall - self._echo_rise) * self.speed_of_sound / 2.0
self._echo_fall = None
self._echo_rise = None
return min(1.0, distance / self._max_distance) return min(1.0, distance / self._max_distance)
else: else:
# If we only saw one edge it means we missed the echo because # If we only saw one edge it means we missed the echo because