Add autolux

adafruit_veml7700.py

@@ -31,6 +31,8 @@
  https://github.com/adafruit/Adafruit_CircuitPython_Register
 """
 
+import time
+
 from micropython import const
 import adafruit_bus_device.i2c_device as i2cdevice
 from adafruit_register.i2c_struct import UnaryStruct, ROUnaryStruct
@@ -78,6 +80,9 @@ class VEML7700:
  ALS_GAIN_1_8: 0.125,
  }
 
+ # Convenience list of gains
+ gain_settings = [ALS_GAIN_1_8, ALS_GAIN_1_4, ALS_GAIN_1, ALS_GAIN_2]
+
  # Integration time value integers
  integration_time_values = {
  ALS_25MS: 25,
@@ -88,6 +93,16 @@ class VEML7700:
  ALS_800MS: 800,
  }
 
+ # Convenience list of integration times
+ integration_time_settings = [
+ ALS_25MS,
+ ALS_50MS,
+ ALS_100MS,
+ ALS_200MS,
+ ALS_400MS,
+ ALS_800MS,
+ ]
+
  # ALS - Ambient light sensor high resolution output data
  light = ROUnaryStruct(0x04, "<H")
  """Ambient light data.
@@ -146,7 +161,7 @@ class VEML7700:
  import adafruit_veml7700
 
  i2c = board.I2C() # uses board.SCL and board.SDA
- veml7700 = adafruit_vcnl4040.VCNL4040(i2c)
+ veml7700 = adafruit_veml7700.VEML7700(i2c)
 
  veml7700.light_gain = veml7700.ALS_GAIN_2
 
@@ -169,7 +184,7 @@ class VEML7700:
  import adafruit_veml7700
 
  i2c = board.I2C() # uses board.SCL and board.SDA
- veml7700 = adafruit_vcnl4040.VCNL4040(i2c)
+ veml7700 = adafruit_veml7700.VEML7700(i2c)
 
  veml7700.light_integration_time = veml7700.ALS_400MS
 
@@ -205,6 +220,33 @@ def __init__(self, i2c_bus: I2C, address: int = 0x10) -> None:
  else:
  raise RuntimeError("Unable to enable VEML7700 device")
 
+ self.last_read = self.milliseconds()
+
+ @staticmethod
+ def milliseconds() -> float:
+ """The time in milliseconds.
+
+ :return: The current time.
+ :rtype: float
+ """
+ return time.monotonic() * 1000
+
+ def compute_lux(self, als: int, use_correction: bool) -> float:
+ """Compute lux, possibly using non-linear correction.
+
+ :param int als: The ambient light level.
+ :param bool use_correction: Flag for applying the non-linear correction.
+
+ :return: The calculated lux.
+ :rtype: float
+ """
+ lux = self.resolution() * als
+ if use_correction:
+ lux = (
+ ((6.0135e-13 * lux - 9.3924e-9) * lux + 8.1488e-5) * lux + 1.0023
+ ) * lux
+ return lux
+
  def integration_time_value(self) -> int:
  """Integration time value in integer form. Used for calculating :meth:`resolution`."""
  integration_time = self.light_integration_time
@@ -253,3 +295,77 @@ def lux(self) -> float:
  time.sleep(0.1)
  """
  return self.resolution() * self.light
+
+ @property
+ def autolux(self) -> float:
+ """Light value in lux using auto checks and correction.
+
+ This property uses auto gain and auto integration time adjustments as well
+ as a non-linear correction if necessary.
+
+ .. code-block:: python
+
+ import time
+ import board
+ import adafruit_veml7700
+
+ i2c = board.I2C() # uses board.SCL and board.SDA
+ veml7700 = adafruit_veml7700.VEML7700(i2c)
+
+ while True:
+ print("Lux:", veml7700.autolux)
+ veml7700.wait_autolux(0.1)
+ """
+ gain_index = 0
+ it_index = 2
+ use_correction = False
+
+ self.gain_settings.index(self.light_gain)
+ self.integration_time_settings.index(self.light_integration_time)
+
+ als = self._read_als_wait()
+
+ if als <= 100:
+ while als <= 100 and not (gain_index == 3 and it_index == 5):
+ if gain_index < 3:
+ gain_index += 1
+ self.light_gain = self.gain_settings[gain_index]
+ elif it_index < 5:
+ it_index += 1
+ self.light_integration_time = self.integration_time_settings[
+ it_index
+ ]
+ als = self._read_als_wait()
+ else:
+ use_correction = True
+ while als > 10000 and it_index > 0:
+ it_index -= 1
+ self.light_integration_time = self.integration_time_settings[it_index]
+ als = self._read_als_wait()
+
+ return self.compute_lux(als, use_correction)
+
+ def _read_als_wait(self) -> float:
+ """Read ambient light level, but wait on the integration time.
+
+ :return: The ambient light level value.
+ :rtype: float
+ """
+ time_to_wait = 2 * self.integration_time_value()
+ time_waited = self.milliseconds() - self.last_read
+ if time_waited < time_to_wait:
+ time.sleep((time_to_wait - time_waited) / 1000)
+ self.last_read = self.milliseconds()
+ return self.light
+
+ def wait_autolux(self, wait_time: float) -> None:
+ """Wait minimum time between autolux measurements.
+
+ Ensure that the shortest wait time cannot be below the current
+ integration time setting.
+
+ :param float wait_time: The requested time between measurements (seconds).
+ """
+ minimum_wait_time = self.integration_time_value() / 1000
+ actual_wait_time = max(minimum_wait_time, wait_time)
+ time.sleep(actual_wait_time)