diff --git a/pysense/lib/LTR329ALS01.py b/pysense/lib/LTR329ALS01.py
index 748aa54..0c6ce6a 100644
--- a/pysense/lib/LTR329ALS01.py
+++ b/pysense/lib/LTR329ALS01.py
@@ -18,6 +18,14 @@ class LTR329ALS01:
     ALS_GAIN_8X = const(0x03)
     ALS_GAIN_48X = const(0x06)
     ALS_GAIN_96X = const(0x07)
+    ALS_GAIN_VALUES = {
+        ALS_GAIN_1X: 1,
+        ALS_GAIN_2X: 2,
+        ALS_GAIN_4X: 4,
+        ALS_GAIN_8X: 8,
+        ALS_GAIN_48X: 48,
+        ALS_GAIN_96X: 96
+    }
 
     ALS_INT_50 = const(0x01)
     ALS_INT_100 = const(0x00)
@@ -27,6 +35,16 @@ class LTR329ALS01:
     ALS_INT_300 = const(0x06)
     ALS_INT_350 = const(0x07)
     ALS_INT_400 = const(0x03)
+    ALS_INT_VALUES = {
+        ALS_INT_50: 0.5,
+        ALS_INT_100: 1,
+        ALS_INT_150: 1.5,
+        ALS_INT_200: 2,
+        ALS_INT_250: 2.5,
+        ALS_INT_300: 3,
+        ALS_INT_350: 3.5,
+        ALS_INT_400: 4
+    }
 
     ALS_RATE_50 = const(0x00)
     ALS_RATE_100 = const(0x01)
@@ -41,6 +59,9 @@ def __init__(self, pysense = None, sda = 'P22', scl = 'P21', gain = ALS_GAIN_1X,
         else:
             self.i2c = I2C(0, mode=I2C.MASTER, pins=(sda, scl))
 
+        self.gain = gain
+        self.integration = integration
+
         contr = self._getContr(gain)
         self.i2c.writeto_mem(ALS_I2CADDR, ALS_CONTR_REG, bytearray([contr]))
 
@@ -68,3 +89,19 @@ def light(self):
         data0 = int(self._getWord(ch0high[0], ch0low[0]))
 
         return (data0, data1)
+
+    def lux(self):
+        # Calculate Lux value from formular in Appendix A of the datasheet
+        light_level = self.light()
+        if light_level[0]+light_level[1] > 0:
+            ratio = light_level[1]/(light_level[0]+light_level[1])
+            if ratio < 0.45:
+                return (1.7743 * light_level[0] + 1.1059 * light_level[1]) / self.ALS_GAIN_VALUES[self.gain] / self.ALS_INT_VALUES[self.integration]
+            elif ratio < 0.64 and ratio >= 0.45:
+                return (4.2785 * light_level[0] - 1.9548 * light_level[1]) / self.ALS_GAIN_VALUES[self.gain] / self.ALS_INT_VALUES[self.integration]
+            elif ratio < 0.85 and ratio >= 0.64:
+                return (0.5926 * light_level[0] + 0.1185 * light_level[1]) / self.ALS_GAIN_VALUES[self.gain] / self.ALS_INT_VALUES[self.integration]
+            else:
+                return 0
+        else:
+            return 0
diff --git a/pysense/lib/MPL3115A2.py b/pysense/lib/MPL3115A2.py
index ecea6e0..fbe9b25 100644
--- a/pysense/lib/MPL3115A2.py
+++ b/pysense/lib/MPL3115A2.py
@@ -69,8 +69,10 @@ def __init__(self, pysense = None, sda = 'P22', scl = 'P21', mode = PRESSURE):
             raise MPL3115A2exception("Error with MPL3115A2")
 
     def _read_status(self):
-        while True:
+        read_attempts = 0
+        while read_attempts < 500:
             self.i2c.readfrom_mem_into(MPL3115_I2CADDR, MPL3115_STATUS, self.STA_reg)
+            read_attempts += 1
 
             if(self.STA_reg[0] == 0):
                 time.sleep(0.01)
@@ -80,6 +82,11 @@ def _read_status(self):
             else:
                 return False
 
+        # If we get here the sensor isn't responding.  Reset it so next time in it should work
+        self.i2c.writeto_mem(MPL3115_I2CADDR, MPL3115_CTRL_REG1, bytes([0x00])) # put into standby
+        self.i2c.writeto_mem(MPL3115_I2CADDR, MPL3115_CTRL_REG1, bytes([0x04])) # reset
+        return False
+
     def pressure(self):
         if self.mode == ALTITUDE:
             raise MPL3115A2exception("Incorrect Measurement Mode MPL3115A2")
diff --git a/pysense/lib/SI7006A20.py b/pysense/lib/SI7006A20.py
index 0246f86..5f89f5c 100644
--- a/pysense/lib/SI7006A20.py
+++ b/pysense/lib/SI7006A20.py
@@ -12,8 +12,18 @@ class SI7006A20:
 
     SI7006A20_I2C_ADDR = const(0x40)
 
+    # I2C commands
     TEMP_NOHOLDMASTER = const(0xF3)
     HUMD_NOHOLDMASTER = const(0xF5)
+    WRITE_USER_REG1 = const(0xE6)
+    READ_USER_REG1 = const(0xE7)
+    WRITE_HEATER_CTRL_REG = const(0x51)
+    READ_HEATER_CTRL_REG = const(0x11)
+
+    # Register masks and offsets
+    USER_REG1_HTR_ENABLE_MASK = const(0b00000100)
+    USER_REG1_HTR_ENABLE_OFFSET = const(0x02)
+    HTR_CTRL_REG_MASK = const(0b00001111)
 
     def __init__(self, pysense = None, sda = 'P22', scl = 'P21'):
         if pysense is not None:
@@ -45,18 +55,32 @@ def humidity(self):
 
     def read_user_reg(self):
         """ reading the user configuration register """
-        self.i2c.writeto(SI7006A20_I2C_ADDR, bytearray([0xE7]))
+        self.i2c.writeto(SI7006A20_I2C_ADDR, bytearray([READ_USER_REG1]))
         time.sleep(0.5)
         data = self.i2c.readfrom(SI7006A20_I2C_ADDR, 1)
         return data[0]
 
     def read_heater_reg(self):
         """ reading the heater configuration register """
-        self.i2c.writeto(SI7006A20_I2C_ADDR, bytearray([0x11]))
+        self.i2c.writeto(SI7006A20_I2C_ADDR, bytearray([READ_HEATER_CTRL_REG]))
         time.sleep(0.5)
         data = self.i2c.readfrom(SI7006A20_I2C_ADDR, 1)
         return data[0]
 
+    def write_heater_reg(self, heater_value):
+        """ writing the heater configuration register """
+        # We should only set the bottom four bits of this register
+        heater_setting = heater_value & HTR_CTRL_REG_MASK
+        self.write_reg(WRITE_HEATER_CTRL_REG, heater_setting)
+
+    def heater_control(self, on_off):
+        """ turn the heater on or off """
+        # Get current settings for everything else
+        user_reg = self.read_user_reg()
+        # Set the heater bit
+        user_reg = (user_reg & ~USER_REG1_HTR_ENABLE_MASK) | (on_off << USER_REG1_HTR_ENABLE_OFFSET)
+        self.write_reg(WRITE_USER_REG1, user_reg)
+
     def read_electronic_id(self):
         """ reading electronic identifier """
         self.i2c.writeto(SI7006A20_I2C_ADDR, bytearray([0xFA]) + bytearray([0x0F]))