added SMBus Lux meter support

backend/sensors.py

@@ -4,7 +4,7 @@
 
 import serial as ser
 import pandas as pd
-from threading import Timer
+import smbus2
 from sys import exit as ex
 import time
 
@@ -22,7 +22,7 @@ class Spectrometer:
             if rstring == 'ERROR':
                 raise Exception #sensor is in error state
         except:
-            print('An exception ocurred when performing spectrometer handshake')
+            raise Exception('An exception ocurred when performing spectrometer handshake')
             ex(1)
         self.setParameters()
 
@@ -52,39 +52,111 @@ class Spectrometer:
                 self.serialObject.write('ATLED3={}\n'.format(led).encode())
                 self.serialObject.readline()
         except:
-           print('An exception occured during spectrometer initialization')
+           raise Exception('An exception occured during spectrometer initialization')
            ex(1)
 
-    def startDataCollection(self):
+    def refreshData(self):
         try:
             self.serialObject.write(b'ATCDATA\n')
             rawresp = self.serialObject.readline().decode()
         except:
-            print('An exception occurred when polling for spectrometer data')
+            raise Exception('An exception occurred when polling for spectrometer data')
             ex(1)
         else:
             responseorder = [i for i in 'RSTUVWGHIJKLABCDEF']
             realorder = [i for i in 'ABCDEFGHRISJTUVWKL']
             response = pd.Series([float(i)/35.0 for i in rawresp[:-3].split(',')], index=responseorder)
             self.data = pd.DataFrame(response, index=realorder, columns = ['uW/cm^2'])
-        self.schedule(self.rrate)
-
-    def schedule(self, refresh):
-        self.timerObject = Timer(refresh, self.startDataCollection)
-        self.timerObject.start()
 
 
     def __init__(self, path='/dev/ttyUSB0', baudrate=115200, tout=1, rrate=1, params={}):
         self.path = path
         self.baudrate = baudrate
         self.timeout = 1
-        self.rrate = rrate
         self.parameters = params
         try:
             self.serialObject = ser.Serial(path, baudrate, timeout=tout)
         except:
-            print('An exception occured when opening the serial port at {}'.format(path))
+            raise Exception('An exception occured when opening the serial port at {}'.format(path))
             ex(1)
         else:
             self.initializeSensor()
             self.startDataCollection()
+
+
+class LxMeter:
+    def __init__(self, busNumber=1, addr=0x39):
+        self.addr = address
+        try:
+            self.bus = smbus2.SMBus(busNumber) # initialize the SMBus interface
+        except:
+            raise Exception('An exception occured opening the SMBus {}'.format(self.bus))
+
+        try:
+            self.bus.write_byte_data(addr, 0xa0, 0x03) # enable the sensor
+        except:
+            raise Exception('An exception occured when enabling lux meter')
+
+    def setGain(self, gain):
+        '''Set the sensor gain. Either 1 or 16.'''
+        if gain == 1:
+            try:
+                temp = self.bus.read_byte_data(addr, 0xa1)
+                self.bus.write_byte_data(addr, 0xa1, 0xef & temp)
+            except:
+                raise Exception('An exception occured when setting lux meter gain')
+        if gain == 16:
+            try:
+                temp = self.bus.read_byte_data(addr, 0xa1)
+                self.bus.write_byte_data(addr, 0xa1, 0x10 | temp)
+            except:
+                raise Exception('An exception occured when setting lux meter gain')
+        else:
+            raise Exception('Invalid gain')
+
+    def getGain(self):
+        '''Get the gain from the sensor.'''
+        try:
+            if self.bus.read_byte_data(addr, 0xa1) & 0x10 == 0x10:
+                return 16
+            if self.bus.read_byte_data(addr, 0xa1) & 0x10 == 0x00:
+                return 1
+        except:
+            raise Exception('An error occured when getting lux meter gain')
+
+    def setIntTime(self, time):
+        '''Set the lux sensor integration time. 0 to including 2'''
+        if time < 0 or time > 2:
+            raise Exception('Invalid integration time')
+        try:
+            temp = self.bus.read_byte_data(addr, 0xa1)
+            self.bus.write_byte_data(addr, 0xa1, (temp & 0xfc) | time)
+        except:
+            raise Exception('An error occured setting lux integration time')
+
+    def getIntTime(self):
+        '''Get the lux sensor integration time.'''
+        try:
+            return self.bus.read_byte_data(addr, 0xa1) & 0xfc
+        except:
+            raise Exception('An error occured getting lux integration time')
+
+    def getData(self):
+        '''return the calculated lux value'''
+        try:
+            chA = self.bus.read_word_data(addr, 0xac)
+            chB = self.bus.read_word_data(addr, 0xae)
+        except:
+            raise Exception('An error occured fetching lux channels')
+
+        if chB/chA <= 0.5 and chB/chA > 0:
+            lux = (0.0304*chA) - (0.062*chA*((chB/chA)**1.4))
+        else if chB/chA <= 0.61 and chB/chA > 0.5:
+            lux = (0.0224*chA) - (0.031*chB)
+        else if chB/chA <=0.8 and chB/chA > 0.61:
+            lux = (0.0128*chA) - (0.0153*chB)
+        else if chB/chA <=1.3 and chB/chA >0.8:
+            lux = (0.00146*chA) - (0.00112*chB)
+        else:
+            lux = 0
+        return lux