API Reference

adafruit_ltr390

Adafruit CircuitPython library for the LTR390

  • Author(s): Bryan Siepert

Implementation Notes

Hardware:

Software and Dependencies:

class adafruit_ltr390.Gain

Options for gain

Gain

Raw Measurement Multiplier

Gain.GAIN_1X

1

Gain.GAIN_3X

3

Gain.GAIN_6X

6

Gain.GAIN_9X

9

Gain.GAIN_18X

18
class adafruit_ltr390.LTR390(i2c: I2C, address: int = 83)

Class to use the LTR390 Ambient Light and UV sensor

Parameters:

  • i2c (I2C) – The I2C bus the LTR390 is connected to.

  • address (int) – The I2C device address. Defaults to 0x53

Quickstart: Importing and using the LTR390

Here is an example of using the LTR390 class. First you will need to import the libraries to use the sensor

import board
import adafruit_ltr390

Once this is done you can define your board.I2C object and define your sensor object

i2c = board.I2C()  # uses board.SCL and board.SDA
ltr = adafruit_ltr390.LTR390(i2c)

Now you have access to the lux and light attributes

lux = ltr.lux
light = ltr.light
data_ready

Ask the sensor if new data is available

enable_alerts(enable: bool, source: bool, persistance: int) → None

The configuration of alerts raised by the sensor

Parameters:

  • enable – Whether the interrupt output is enabled

  • source – Whether to use the ALS or UVS data register to compare

  • persistance – The number of consecutive out-of-range readings before

property gain: int

The amount of gain the raw measurements are multiplied by

high_threshold

When the measured value is more than the low_threshold, the sensor will raise an alert

initialize() → None

Reset the sensor to it’s initial unconfigured state and configure it with sensible defaults so it can be used

property light: int

The currently measured ambient light level

low_threshold

When the measured value is less than the low_threshold, the sensor will raise an alert

property lux: float

Read light level and return calculated Lux value.

property measurement_delay: int

The delay between measurements. This can be used to set the measurement rate which affects the sensor power usage.

property resolution: int

Set the precision of the internal ADC used to read the light measurements

threshold_passed

The status of any configured alert. If True, a threshold has been passed.

Once read, this property will be False until it is updated in the next measurement cycle

property uvi: float

Read UV count and return calculated UV Index (UVI) value based upon the rated sensitivity of 1 UVI per 2300 counts at 18X gain factor and 20-bit resolution.

property uvs: int

The calculated UV value

property window_factor: float

Window transmission factor (Wfac) for UVI and Lux calculations. A factor of 1 (default) represents no window or clear glass; > 1 for a tinted window. Factor of > 1 requires an empirical calibration with a reference light source.

class adafruit_ltr390.MeasurementDelay

Options for measurement_delay

MeasurementDelay

Time Between Measurement Cycles (ms)

MeasurementDelay.DELAY_25MS

25

MeasurementDelay.DELAY_50MS

50

MeasurementDelay.DELAY_100MS

100

MeasurementDelay.DELAY_200MS

200

MeasurementDelay.DELAY_500MS

500

MeasurementDelay.DELAY_1000MS

1000

MeasurementDelay.DELAY_2000MS

2000
class adafruit_ltr390.Resolution

Options for resolution

Resolution

Internal ADC Resolution

Resolution.RESOLUTION_13BIT

13 bits

Resolution.RESOLUTION_16BIT

16 bits

Resolution.RESOLUTION_17BIT

17 bits

Resolution.RESOLUTION_18BIT

18 bits

Resolution.RESOLUTION_19BIT

19 bits

Resolution.RESOLUTION_20BIT

20 bits