Bh1745 - RGB Sensor

The Bh1745 is a digital color sensor able to detect 3 distinct channels of light (red, green, blue) and is most suitable to obtain the illuminance and color temperature of ambient light. The device can detect light intensity in a range of 0.005 to 40 000 lux.

Documentation

Datasheet of the Bh1745

Usage

Important: make sure you properly setup the I2C pins especially for ESP32 before creating the I2cDevice, make sure you install the nanoFramework.Hardware.ESP32 nuget:

//////////////////////////////////////////////////////////////////////
// when connecting to an ESP32 device, need to configure the I2C GPIOs
// used for the bus
Configuration.SetPinFunction(21, DeviceFunction.I2C1_DATA);
Configuration.SetPinFunction(22, DeviceFunction.I2C1_CLOCK);

For other devices like STM32, please make sure you're using the preset pins for the I2C bus you want to use.

2 examples on how to use this device binding are available in the https://github.com/nanoFramework/nanoFramework.IoT.Device/tree/develop/devices/Bh1745/samples folder.

sensor

The quality of the color measurements is very reliant on the lighting. For accurate color readings it is advisable to calibrate the sensor on first use and to use it under stable lighting conditions.

Some breakout boards come with built in LEDs for this purpose (some of the API functionality may also have been repurposed to control these LEDs).

Basic usage:

using System;
using System.Device.I2c;
using System.Threading;
using Iot.Device.Bh1745;

// bus id on the MCU
const int busId = 1;

// create device
I2cConnectionSettings i2cSettings = new(busId, Bh1745.DefaultI2cAddress);
using I2cDevice i2cDevice = I2cDevice.Create(i2cSettings);
using Bh1745 i2cBh1745 = new Bh1745(i2cDevice);
// wait for first measurement
Thread.Sleep(i2cBh1745.MeasurementTimeAsTimeSpan());

while (true)
{
    var color = i2cBh1745.GetCompensatedColor();
    Debug.WriteLine("RGB color read: #{0:X2}{1:X2}{2:X2}", color.R, color.G, color.B);
    Debug.WriteLine($"Raw illumination value: {i2cBh1745.ReadClearDataRegister()}");

    Thread.Sleep(i2cBh1745.MeasurementTimeAsTimeSpan());
}

Advance usage with configuration:

// bus id on the MCU
const int busId = 1;

// create device
var i2cSettings = new I2cConnectionSettings(busId, Bh1745.DefaultI2cAddress);
var i2cDevice = I2cDevice.Create(i2cSettings);

using Bh1745 i2cBh1745 = new Bh1745(i2cDevice)
{
    // multipliers affect the compensated values
    // ChannelCompensationMultipliers:  Red, Green, Blue, Clear
    ChannelCompensationMultipliers = new(2.5, 0.9, 1.9, 9.5),

    // set custom  measurement time
    MeasurementTime = MeasurementTime.Ms1280,

    // interrupt functionality is detailed in the datasheet
    // Reference: https://www.mouser.co.uk/datasheet/2/348/bh1745nuc-e-519994.pdf (page 13)
    LowerInterruptThreshold = 0xABFF,
    HigherInterruptThreshold = 0x0A10,

    LatchBehavior = LatchBehavior.LatchEachMeasurement,
    InterruptPersistence = InterruptPersistence.UpdateMeasurementEnd,
    InterruptIsEnabled = true,
};

// wait for first measurement
Thread.Sleep(i2cBh1745.MeasurementTimeAsTimeSpan());

while (true)
{
    var color = i2cBh1745.GetCompensatedColor();

    if (!i2cBh1745.ReadMeasurementIsValid())
    {
        Debug.WriteLine("Measurement was not valid!");
        continue;
    }

    Debug.WriteLine("RGB color read: #{0:X2}{1:X2}{2:X2}", color.R, color.G, color.B);
    Debug.WriteLine($"Raw illumination value: {i2cBh1745.ReadClearDataRegister()}");

    Thread.Sleep(i2cBh1745.MeasurementTimeAsTimeSpan());
}

Table of Contents

Bh1745 - RGB Sensor

Documentation

Usage