cwlsxxa: Initial implementation

The driver was developed using the Veris CWLSHTA CO2 Gas sensor.  The
'T' variant supports a temperature sensor, and the 'H' variant
supports a humidity sensor.

All 3 signals are provided by the device as analog 0-5Vdc, 0-10Vdc, or
4-20ma loop current outputs.  For devices supporting temperature, the
valid temperature range is 10C to 50C.  The humidity ranges from 0% to
100% (non-condensing).  The CO2 sensor ranges from 0 to 2000 ppm.

This driver was developed using the 5Vdc outputs and the 4-20ma
outputs.  For voltage outputs, your MCU must be configured for 5V
operation.  In addition, you must configure the sensor (via it's
configuration switches) to output 0-5VDC only.  Using any other analog
reference voltage will require the appropriate external circuitry
(such as a voltage divider) in order to interface safely with your
MCU.

In addition, the sensor can be configured for 4-20ma usage, by
specifying the correct receiver resistance (in ohms) in the
constructor.  This sensor was tested with a Cooking Hacks (Libelium)
4-channel 4-20ma Arduino interface shield.  For this interface, the
receiver resistance was specified as 165.0 ohms.

Signed-off-by: Jon Trulson <jtrulson@ics.com>
Signed-off-by: Abhishek Malik <abhishek.malik@intel.com>

examples/python/cwlsxxa.py

@@ -0,0 +1,61 @@
+#!/usr/bin/python
+# Author: Jon Trulson <jtrulson@ics.com>
+# Copyright (c) 2016 Intel Corporation.
+#
+# 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, sys, signal, atexit
+import pyupm_cwlsxxa as sensorObj
+
+## Exit handlers ##
+# This function stops python from printing a stacktrace when you hit control-C
+def SIGINTHandler(signum, frame):
+	raise SystemExit
+
+# This function lets you run code on exit
+def exitHandler():
+	print "Exiting"
+	sys.exit(0)
+
+# Register exit handlers
+atexit.register(exitHandler)
+signal.signal(signal.SIGINT, SIGINTHandler)
+
+print "Initializing..."
+
+# Instantiate an CWLSXXA instance, using A0 for CO2, A1 for
+# humidity and A2 for temperature
+sensor = sensorObj.CWLSXXA(0, 1, 2)
+
+# update and print available values every second
+while (1):
+        # update our values from the sensor
+        sensor.update()
+
+        # we show both C and F for temperature
+        print "Temperature:", sensor.getTemperature(), "C /",
+        print sensor.getTemperature(True), "F"
+
+        print "Humidity:", sensor.getHumidity(), "%"
+
+        print "CO2:", sensor.getCO2(), "ppm"
+
+        print
+	time.sleep(1)