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Software/Python/grove_co2_sensor/grove_co2_lib.py

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+#!/usr/bin/env python
+########################################################################               # GrovePi Library for using the Grove - CO2 Sensor(http://www.seeedstudio.com/depot/Grove-CO2-Sensor-p-1863.html)
+#
+# The GrovePi connects the Raspberry Pi and Grove sensors.  You can learn more about GrovePi here:  http://www.dexterindustries.com/GrovePi
+#
+# Have a question about this library?  Ask on the forums here:  http://forum.dexterindustries.com/c/grovepi
+#         
+#
+# NOTES:                                      
+# * Calibration and read of the CO2 sensor MH-Z16 according to the datasheet : http://www.seeedstudio.com/wiki/images/c/ca/MH-Z16_CO2_datasheet_EN.pdf
+# * output value directly in ppm
+# * Library derived from the inital controbution by Doms Genoud (@domsgen) here: http://www.dexterindustries.com/topic/how-to-use-co2-grove-sensor-with-serial-grovepi/
+# 
+# History
+# ------------------------------------------------
+# Author     		Date      		Comments
+# Doms Genoud      	13 Apr 15 		Initial Authoring
+# Karan				07 Jan 16		Code cleanup and added to main Github repo
+# 			                                                         
+# These files have been made available online through a Creative Commons Attribution-ShareAlike 3.0  license.
+# (http://creativecommons.org/licenses/by-sa/3.0/)           
+#
+########################################################################
+
+import serial, time
+
+class CO2:
+#inspired from c code of http://www.seeedstudio.com/wiki/Grove_-_CO2_Sensor
+#Gas concentration= high level *256+low level
+    inp = []
+    cmd_zero_sensor = b'\xff\x87\x87\x00\x00\x00\x00\x00\xf2'
+    cmd_span_sensor = b'\xff\x87\x87\x00\x00\x00\x00\x00\xf2'
+    cmd_get_sensor = b'\xff\x01\x86\x00\x00\x00\x00\x00\x79'
+    
+    def __init__(self):	
+        #To open the raspberry serial port
+                ser = serial.Serial('/dev/serial0', 9600, timeout = 1)	#Open the serial port at 9600 baud
+
+        #init serial
+        ser.flush()
+        
+    def read(self):
+        try:
+            ser.write(self.cmd_get_sensor)
+            self.inp = ser.read(9)
+            high_level = self.inp[2]
+            low_level = self.inp[3]
+            temp_co2  = self.inp[4] - 40
+
+            #output in ppm, temp
+            conc = high_level*256+low_level
+            return [conc,temp_co2]
+
+        except IOError:
+            return [-1,-1]
+            
+if __name__ == "__main__":		
+    c = CO2()
+    while True:
+        print(c.read())
+        time.sleep(1)