Fiat lux

veml6070/__init__.py

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+
+from veml6070 import Veml6070
+from veml6070 import INTEGRATIONTIME_1_2T, INTEGRATIONTIME_1T, INTEGRATIONTIME_2T, INTEGRATIONTIME_4T, RSET_240K, RSET_270K, RSET_300K, RSET_600K

veml6070/veml6070.py

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+
+import smbus
+import time
+
+ADDR_L=0x38 # 7bit address of the VEML6070 (write, read)
+ADDR_H=0x39 # 7bit address of the VEML6070 (read)
+
+RSET_240K=240000
+RSET_270K=270000
+RSET_300K=300000
+RSET_600K=600000
+
+SHUTDOWN_DISABLE=0x00
+SHUTDOWN_ENABLE=0x01
+
+INTEGRATIONTIME_1_2T=0x00
+INTEGRATIONTIME_1T=0x01
+INTEGRATIONTIME_2T=0x02
+INTEGRATIONTIME_4T=0x03
+
+class Veml6070:
+
+    def __init__(self, i2c_bus=1, sensor_address=ADDR_L, rset=RSET_270K, integration_time=INTEGRATIONTIME_1T):
+        self.bus = smbus.SMBus(i2c_bus)
+        self.sendor_address = sensor_address
+        self.rset = rset
+        self.shutdown = SHUTDOWN_DISABLE # before set_integration_time()
+        self.set_integration_time(integration_time)
+        self.disable()
+
+    def set_integration_time(self, integration_time):
+        self.integration_time = integration_time
+        self.bus.write_byte(self.sendor_address, self.get_command_byte())
+        # constant offset determined experimentally to allow sensor to readjust
+        time.sleep(0.2)
+
+    def get_integration_time(self):
+        return self.integration_time
+
+    def enable(self):
+        self.shutdown = SHUTDOWN_DISABLE
+        self.bus.write_byte(self.sendor_address, self.get_command_byte())
+
+    def disable(self):
+        self.shutdown = SHUTDOWN_ENABLE
+        self.bus.write_byte(self.sendor_address, self.get_command_byte())
+
+    def get_uva_light_intensity_raw(self):
+        self.enable()
+        # wait two times the refresh time to allow completion of a previous cycle with old settings (worst case)
+        time.sleep(self.get_refresh_time()*2)
+        msb = self.bus.read_byte(self.sendor_address+(ADDR_H-ADDR_L))
+        lsb = self.bus.read_byte(self.sendor_address)
+        self.disable()
+        return (msb << 8) | lsb
+
+    def get_uva_light_intensity(self):
+        uv = self.get_uva_light_intensity_raw()
+        return uv * self.get_uva_light_sensitivity()
+
+    def get_command_byte(self):
+        """
+        assembles the command byte for the current state
+        """
+        cmd = (self.shutdown & 0x01) << 0 # SD
+        cmd = (self.integration_time & 0x03) << 2 # IT
+        cmd = ((cmd | 0x02) & 0x3F) # reserved bits
+        return cmd
+
+    def get_refresh_time(self):
+        """
+        returns time needed to perform a complete measurement using current settings (in s)
+        """
+        case_refresh_rset = {
+            RSET_240K: 0.1,
+            RSET_270K: 0.1125,
+            RSET_300K: 0.125,
+            RSET_600K: 0.25
+        }
+        case_refresh_it = {
+            INTEGRATIONTIME_1_2T: 0.5,
+            INTEGRATIONTIME_1T: 1,
+            INTEGRATIONTIME_2T: 2,
+            INTEGRATIONTIME_4T: 4
+        }
+        return case_refresh_rset[self.rset] * case_refresh_it[self.integration_time]
+
+    def get_uva_light_sensitivity(self):
+        """
+        returns UVA light sensitivity in W/(m*m)/step
+        """
+        case_sens_rset = {
+            RSET_240K: 0.05,
+            RSET_270K: 0.05625,
+            RSET_300K: 0.0625,
+            RSET_600K: 0.125
+        }
+        case_sens_it = {
+            INTEGRATIONTIME_1_2T: 0.5,
+            INTEGRATIONTIME_1T: 1,
+            INTEGRATIONTIME_2T: 2,
+            INTEGRATIONTIME_4T: 4
+        }
+        return case_sens_rset[self.rset] / case_sens_it[self.integration_time]