mwss_light.py

from machine import Pin, I2C
import time

_DEVICE_ADDR = 0x23 # default I2C address for BH1750 light sensor

class LightSensor():
  
  #Light Modes
  OP_SINGLE_HRES1 = 0x20
  OP_SINGLE_HRES2 = 0x21
  OP_SINGLE_LRES = 0x23

  DELAY_HMODE = 180  # 180ms in H-mode
  DELAY_LMODE = 24  # 24ms in L-mode

  i2c = None
  i2c_address = 0
  i2c_transaction_length = 0
  mode = None
  
  def get_sensor_value(self):    
    if self.i2c != None:
      
      self.i2c.writeto(self.i2c_address, b"\x00") # power off
      self._power_up()
      self.set_mode(self.OP_SINGLE_HRES2)  # highest accuracy
      
      results = self.i2c.readfrom(self.i2c_address, self.i2c_transaction_length)
      if results != None and len(results) == self.i2c_transaction_length:
        ch0 = results[0]
        ch1 = results[1]
        return self._data_to_lux(ch0, ch1)
      
    else:
      print ("Problem with response from i2c service: %s" % results)
      return None
    
  def _power_up(self):
    self.i2c.writeto(self.i2c_address, b"\x01")  # power on
    self.i2c.writeto(self.i2c_address, b"\x07")  # reset    
    
  def set_mode(self, mode):
    self.mode = mode
    self.i2c.writeto(self.i2c_address, bytes([self.mode]))  # set measurement mode
    time.sleep_ms(self.DELAY_LMODE if mode == self.OP_SINGLE_LRES else self.DELAY_HMODE)
       
  def _data_to_lux(self, ch0, ch1):
    lux = 0
    if (ch0 == 0):
      return lux
    factor = 2.0 if self.mode==self.OP_SINGLE_HRES2 else 1.0
    lux = (ch0<<8 | ch1) / (1.2 * factor)
    return lux

  def __init__(self):
    self.i2c = I2C(scl=Pin(5), sda=Pin(4))
    self.i2c_address = _DEVICE_ADDR
    self.i2c_transaction_length = 2
    
def main():
  while True:
    time.sleep(5)
    sensor = LightSensor()
    print (sensor.get_sensor_value())

if (__name__ == "__main__"):
  main()