Merge pull request #8 from jerryneedell/jerryn_dht

 modified get_pulses to reduce errors

Author: tannewt

adafruit_dht.py

@@ -100,7 +100,6 @@ def _get_pulses(self):
         pulses will have 81 elements for the DHT11/22 type devices.
         """
         pulses = array.array('H')
-        tmono = time.monotonic()
 
         # create the PulseIn object using context manager
         with pulseio.PulseIn(self._pin, 81, True) as pulse_in:
@@ -115,11 +114,10 @@ def _get_pulses(self):
             pulse_in.resume(self._trig_wait)
 
             # loop until we get the return pulse we need or
-            # time out after 1/2 seconds
+            # time out after 1/4 second
+            tmono = time.monotonic()
             while True:
-                if len(pulse_in) >= 80:
-                    break
-                if time.monotonic()-tmono > 0.5: # time out after 1/2 seconds
+                if time.monotonic()-tmono > 0.25: # time out after 1/4 seconds
                     break
 
             pulse_in.pause()
@@ -137,25 +135,26 @@ def measure(self):
             Raises RuntimeError exception for checksum failure and for insuffcient
             data returned from the device (try again)
         """
-        if time.monotonic()-self._last_called > 0.5:
+        delay_between_readings = 0.5
+        if self._dht11:
+            delay_between_readings = 1.0
+        if time.monotonic()-self._last_called > delay_between_readings:
             self._last_called = time.monotonic()
 
             pulses = self._get_pulses()
-            ##print(pulses)
 
             if len(pulses) >= 80:
                 buf = array.array('B')
                 for byte_start in range(0, 80, 16):
                     buf.append(self._pulses_to_binary(pulses, byte_start, byte_start+16))
-                #print(buf)
 
                 # humidity is 2 bytes
                 if self._dht11:
                     self._humidity = buf[0]
                 else:
                     self._humidity = ((buf[0]<<8) | buf[1]) / 10
 
-                # tempature is 2 bytes
+                # temperature is 2 bytes
                 if self._dht11:
                     self._temperature = buf[2]
                 else:
@@ -170,15 +169,10 @@ def measure(self):
                 if chk_sum & 0xff != buf[4]:
                     # check sum failed to validate
                     raise RuntimeError("Checksum did not validate. Try again.")
-                    #print("checksum did not match. Temp: {} Humidity: {} Checksum:{}"
-                    #.format(self._temperature,self._humidity,bites[4]))
 
-                # checksum matches
-                #print("Temp: {} C Humidity: {}% ".format(self._temperature, self._humidity))
 
             else:
                 raise RuntimeError("A full buffer was not returned.  Try again.")
-                #print("did not get a full return.  number returned was: {}".format(len(r)))
 
     @property
     def temperature(self):