Remarks

Sgp40
Status
Source code	GitHub
Datasheet(s)	GitHub
NuGet package

Code Example

Sgp40? sensor;

public override Task Initialize()
{
    Resolver.Log.Info("Initializing...");

    sensor = new Sgp40(Device.CreateI2cBus());

    Resolver.Log.Info($"Sensor SN: {sensor.SerialNumber:x6}");

    if (sensor.RunSelfTest())
    {
        Resolver.Log.Info("Self test successful");
    }
    else
    {
        Resolver.Log.Warn("Self test failed");
    }

    var consumer = Sgp40.CreateObserver(
        handler: result =>
        {
            Resolver.Log.Info($"Observer: VOC changed by threshold; new index: {result.New}");
        },
        filter: result =>
        {
            //c# 8 pattern match syntax. checks for !null and assigns var.
            return Math.Abs(result.New - result.Old ?? 0) > 10;
        }
    );
    sensor.Subscribe(consumer);

    sensor.Updated += (sender, result) =>
    {
        Resolver.Log.Info($"  VOC: {result.New}");
    };

    return base.Initialize();
}

public override async Task Run()
{
    await ReadConditions();

    sensor?.StartUpdating(TimeSpan.FromSeconds(1));
}

async Task ReadConditions()
{
    if(sensor == null) { return; }

    var result = await sensor.Read();
    Resolver.Log.Info("Initial Readings:");
    Resolver.Log.Info($"  Temperature: {result}");
}

Sample project(s) available on GitHub

Wiring Example

To wire a Sgp40 to your Meadow board, connect the following:

Sgp40	Meadow Pin
GND	GND
SCL	D08 (SCL)
SDA	D07 (SDA)
VCC	3V3

Characteristic	Locus
Inheritance	System.Object ObservableBase<System.Int32> SamplingSensorBase<System.Int32> PollingSensorBase<System.Int32> ByteCommsSensorBase<System.Int32> > Sgp40
Implements	ISamplingSensor<System.Int32> ISamplingSensor<System.Int32> IDisposable
Inherited Members	ByteCommsSensorBase<Int32>.Peripheral ByteCommsSensorBase<Int32>.ReadBuffer ByteCommsSensorBase<Int32>.WriteBuffer ByteCommsSensorBase<Int32>.Init(Int32, Int32) ByteCommsSensorBase<Int32>.Dispose(Boolean) ByteCommsSensorBase<Int32>.Dispose() PollingSensorBase<Int32>.StartUpdating(Nullable<TimeSpan>) PollingSensorBase<Int32>.StopUpdating() SamplingSensorBase<Int32>.samplingLock SamplingSensorBase<Int32>.Updated SamplingSensorBase<Int32>.SamplingTokenSource SamplingSensorBase<Int32>.Conditions SamplingSensorBase<Int32>.IsSampling SamplingSensorBase<Int32>.UpdateInterval SamplingSensorBase<Int32>.RaiseEventsAndNotify(IChangeResult<>) SamplingSensorBase<Int32>.Read() ObservableBase<Int32>.observers ObservableBase<Int32>.NotifyObservers(IChangeResult<>) Meadow.Foundation.ObservableBase<System.Int32>.Subscribe(IObserver<>) Meadow.Foundation.ObservableBase<System.Int32>.CreateObserver(Action<>, System.Nullable<Predicate<IChangeResult<UNIT>>>)
Namespace	Meadow.Foundation.Sensors.Atmospheric
Assembly	Sgp40.dll

Syntax

public class Sgp40 : ByteCommsSensorBase<int>, ISamplingSensor<int>, ISamplingSensor<int>, IDisposable

Constructors

Sgp40(II2cBus, Byte)

Creates a new SGP40 VOC sensor.

Declaration

public Sgp40(II2cBus i2cBus, byte address = null)

Parameters

Type	Name	Description
II2cBus	i2cBus	I2CBus.
System.Byte	address	Sensor address (default to 0x40).

Properties

SerialNumber

Serial number of the device.

Declaration

public ulong SerialNumber { get; }

Property Value

Type	Description
System.UInt64

VocIndex

The VOC Index, from the last reading.

Declaration

public int VocIndex { get; }

Property Value

Type	Description
System.Int32

Methods

ClearCompensationData()

Clear the compensation data

Declaration

public void ClearCompensationData()

Initialize()

Initalize the sensor

Declaration

protected void Initialize()

RaiseEventsAndNotify(IChangeResult<Int32>)

Inheritance-safe way to raise events and notify observers.

Declaration

protected override void RaiseEventsAndNotify(IChangeResult<int> changeResult)

Parameters

Type	Name	Description
IChangeResult<System.Int32>	changeResult

ReadSensor()

Reads data from the sensor

Declaration

protected override Task<int> ReadSensor()

Returns

Type	Description
Task<System.Int32>	The latest sensor reading

Overrides

Meadow.Foundation.SamplingSensorBase<System.Int32>.ReadSensor()

RunSelfTest()

This command triggers the built-in self-test checking for integrity of both hotplate and MOX material

Declaration

public bool RunSelfTest()

Returns

Type	Description
System.Boolean	true on sucessful test, otherwise false

SetCompensationData(RelativeHumidity, Units.Temperature)

Set the compensation data

Declaration

public void SetCompensationData(RelativeHumidity humidity, Units.Temperature temperature)

Parameters

Type	Name	Description
RelativeHumidity	humidity	Humidity compensation
Units.Temperature	temperature	Temperature compensation

TurnHeaterOff()

This command turns the hotplate off and stops the measurement. Subsequently, the sensor enters idle mode.

Declaration

public void TurnHeaterOff()

Events

VocIndexUpdated

Declaration

public event EventHandler<ChangeResult<int>> VocIndexUpdated

Event Type

Type	Description
EventHandler<ChangeResult<System.Int32>>