Merge pull request #46 from adafruit/pulseio-fix

Deinitialize pulsein object on exit, gave option to choose whether or not to use pulseio

Author: kattni

adafruit_dht.py

@@ -30,6 +30,7 @@
 
 import array
 import time
+from os import uname
 from digitalio import DigitalInOut, Pull, Direction
 
 _USE_PULSEIO = False
@@ -51,23 +52,33 @@ class DHTBase:
 
     __hiLevel = 51
 
-    def __init__(self, dht11, pin, trig_wait):
+    def __init__(self, dht11, pin, trig_wait, use_pulseio):
         """
         :param boolean dht11: True if device is DHT11, otherwise DHT22.
         :param ~board.Pin pin: digital pin used for communication
         :param int trig_wait: length of time to hold trigger in LOW state (microseconds)
+        :param boolean use_pulseio: False to force bitbang when pulseio available (only with Blinka)
         """
         self._dht11 = dht11
         self._pin = pin
         self._trig_wait = trig_wait
         self._last_called = 0
         self._humidity = None
         self._temperature = None
+        self._use_pulseio = use_pulseio
+        if "Linux" not in uname() and not self._use_pulseio:
+            raise Exception("Bitbanging is not supported when using CircuitPython.")
         # We don't use a context because linux-based systems are sluggish
         # and we're better off having a running process
-        if _USE_PULSEIO:
+        if self._use_pulseio:
             self.pulse_in = PulseIn(self._pin, 81, True)
 
+    def exit(self):
+        """ Cleans up the PulseIn process. Must be called explicitly """
+        if self._use_pulseio:
+            print("De-initializing self.pulse_in")
+            self.pulse_in.deinit()
+
     def _pulses_to_binary(self, pulses, start, stop):
         """Takes pulses, a list of transition times, and converts
         them to a 1's or 0's.  The pulses array contains the transition times.
@@ -108,7 +119,7 @@ def _get_pulses_pulseio(self):
         pulses will have 81 elements for the DHT11/22 type devices.
         """
         pulses = array.array("H")
-        if _USE_PULSEIO:
+        if self._use_pulseio:
             # The DHT type device use a specialize 1-wire protocol
             # The microprocessor first sends a LOW signal for a
             # specific length of time.  Then the device sends back a
@@ -183,7 +194,7 @@ def measure(self):
             new_temperature = 0
             new_humidity = 0
 
-            if _USE_PULSEIO:
+            if self._use_pulseio:
                 pulses = self._get_pulses_pulseio()
             else:
                 pulses = self._get_pulses_bitbang()
@@ -259,8 +270,8 @@ class DHT11(DHTBase):
         :param ~board.Pin pin: digital pin used for communication
     """
 
-    def __init__(self, pin):
-        super().__init__(True, pin, 18000)
+    def __init__(self, pin, use_pulseio=_USE_PULSEIO):
+        super().__init__(True, pin, 18000, use_pulseio)
 
 
 class DHT22(DHTBase):
@@ -269,5 +280,5 @@ class DHT22(DHTBase):
         :param ~board.Pin pin: digital pin used for communication
     """
 
-    def __init__(self, pin):
-        super().__init__(False, pin, 1000)
+    def __init__(self, pin, use_pulseio=_USE_PULSEIO):
+        super().__init__(False, pin, 1000, use_pulseio)

examples/dht_simpletest.py

@@ -5,6 +5,11 @@
 # Initial the dht device, with data pin connected to:
 dhtDevice = adafruit_dht.DHT22(board.D18)
 
+# you can pass DHT22 use_pulseio=False if you wouldn't like to use pulseio.
+# This may be necessary on a Linux single board computer like the Raspberry Pi,
+# but it will not work in CircuitPython.
+# dhtDevice = adafruit_dht.DHT22(board.D18, use_pulseio=False)
+
 while True:
     try:
         # Print the values to the serial port
@@ -20,5 +25,10 @@
     except RuntimeError as error:
         # Errors happen fairly often, DHT's are hard to read, just keep going
         print(error.args[0])
+        time.sleep(2.0)
+        continue
+    except Exception as error:
+        dhtDevice.exit()
+        raise error
 
     time.sleep(2.0)