added temperature reader

controller/drivers/adafruit/Adafruit_DHT/common.py

@@ -0,0 +1,94 @@
+# Copyright (c) 2014 Adafruit Industries
+# Author: Tony DiCola
+
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+import time
+
+import platform_detect
+
+
+# Define error constants.
+DHT_SUCCESS        =  0
+DHT_ERROR_TIMEOUT  = -1
+DHT_ERROR_CHECKSUM = -2
+DHT_ERROR_ARGUMENT = -3
+DHT_ERROR_GPIO     = -4
+TRANSIENT_ERRORS = [DHT_ERROR_CHECKSUM, DHT_ERROR_TIMEOUT]
+
+# Define sensor type constants.
+DHT11  = 11
+DHT22  = 22
+AM2302 = 22
+SENSORS = [DHT11, DHT22, AM2302]
+
+
+def get_platform():
+	"""Return a DHT platform interface for the currently detected platform."""
+	plat = platform_detect.platform_detect()
+	if plat == platform_detect.RASPBERRY_PI:
+		# Check for version 1 or 2 of the pi.
+		version = platform_detect.pi_version()
+		if version == 1:
+			import Raspberry_Pi
+			return Raspberry_Pi
+		elif version == 2:
+			import Raspberry_Pi_2
+			return Raspberry_Pi_2
+		else:
+			raise RuntimeError('No driver for detected Raspberry Pi version available!')
+	elif plat == platform_detect.BEAGLEBONE_BLACK:
+		import Beaglebone_Black
+		return Beaglebone_Black
+	else:
+		raise RuntimeError('Unknown platform.')
+
+def read(sensor, pin, platform=None):
+	"""Read DHT sensor of specified sensor type (DHT11, DHT22, or AM2302) on 
+	specified pin and return a tuple of humidity (as a floating point value
+	in percent) and temperature (as a floating point value in Celsius). Note that
+	because the sensor requires strict timing to read and Linux is not a real
+	time OS, a result is not guaranteed to be returned!  In some cases this will
+	return the tuple (None, None) which indicates the function should be retried.
+	Also note the DHT sensor cannot be read faster than about once every 2 seconds.
+	Platform is an optional parameter which allows you to override the detected
+	platform interface--ignore this parameter unless you receive unknown platform
+	errors and want to override the detection.
+	"""
+	if sensor not in SENSORS:
+		raise ValueError('Expected DHT11, DHT22, or AM2302 sensor value.')
+	if platform is None:
+		platform = get_platform()
+	return platform.read(sensor, pin)
+
+def read_retry(sensor, pin, retries=15, delay_seconds=2, platform=None):
+	"""Read DHT sensor of specified sensor type (DHT11, DHT22, or AM2302) on 
+	specified pin and return a tuple of humidity (as a floating point value
+	in percent) and temperature (as a floating point value in Celsius).
+	Unlike the read function, this read_retry function will attempt to read
+	multiple times (up to the specified max retries) until a good reading can be 
+	found. If a good reading cannot be found after the amount of retries, a tuple
+	of (None, None) is returned. The delay between retries is by default 2
+	seconds, but can be overridden.
+	"""
+	for i in range(retries):
+		humidity, temperature = read(sensor, pin, platform)
+		if humidity is not None and temperature is not None:
+			return (humidity, temperature)
+		time.sleep(delay_seconds)
+	return (None, None)