Meadow.Foundation.Sensors.Atmospheric.Si70xx

Si70xx
Status
Source code	GitHub
Datasheet(s)	GitHub
NuGet package

The SI70xx is a humidity and temperature sensor controlled via I2C.

• ± 3% RH (max)
• 0–80% RH
• High Accuracy Temperature Sensor ±0.4 °C
• –10 to 85 °C
• 0 to 100% RH operating range
• Up to –40 to +125 °C operating range
• Wide operating voltage (1.9 to 3.6 V)
• Low Power Consumption
• 150 µA active current
• 60 nA standby current

Purchasing

The Si7021 is available on a breakout board from the the following suppliers:

• Adafruit Si7021 Breakout Board
• Sparkfun Si7021 Breakout Board
• Tessel Climate Module

Code Example

Si70xx? sensor;

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

    sensor = new Si70xx(Device.CreateI2cBus());

    var consumer = Si70xx.CreateObserver(
        handler: result =>
        {
            Resolver.Log.Info($"Observer: Temp changed by threshold; new temp: {result.New.Temperature?.Celsius:N2}C, old: {result.Old?.Temperature?.Celsius:N2}C");
        },
        filter: result =>
        {
            if (result.Old?.Temperature is { } oldTemp &&
                result.Old?.Humidity is { } oldHumidity &&
                result.New.Temperature is { } newTemp &&
                result.New.Humidity is { } newHumidity)
            {
                return ((newTemp - oldTemp).Abs().Celsius > 0.5 &&
                        (newHumidity - oldHumidity).Percent > 0.05);
            }
            return false;
        }
    );
    sensor.Subscribe(consumer);

    sensor.Updated += (sender, result) =>
    {
        Resolver.Log.Info($"  Temperature: {result.New.Temperature?.Celsius:F1}C");
        Resolver.Log.Info($"  Relative Humidity: {result.New.Humidity:F1}%");
    };

    return Task.CompletedTask;
}

public override async Task Run()
{
    if (sensor == null) { return; }

    var result = await sensor.Read();
    Resolver.Log.Info("Initial Readings:");
    Resolver.Log.Info($"  Temperature: {result.Temperature?.Celsius:F1}C");
    Resolver.Log.Info($"  Relative Humidity: {result.Humidity:F1}%");

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

Sample project(s) available on GitHub

Wiring Example

To wire a Si7021 to your Meadow board, connect the following:

Si7021	Meadow Pin
GND	GND
SCL	D08 (SCL)
SDA	D07 (SDA)
VCC	3V3

It should look like the following diagram:

Class Si70xx

Provide access to the Si70xx series (Si7020, Si7021, and Si7030) temperature and humidity sensors

Assembly: Si70xx.dll

View Source

Declaration

public class Si70xx : ByteCommsSensorBase<(Temperature? Temperature, RelativeHumidity? Humidity)>, IObservable<IChangeResult<(Temperature? Temperature, RelativeHumidity? Humidity)>>, ISamplingSensor<(Temperature? Temperature, RelativeHumidity? Humidity)>, ISensor<(Temperature? Temperature, RelativeHumidity? Humidity)>, IDisposable, ITemperatureSensor, ISamplingSensor<Temperature>, ISensor<Temperature>, IHumiditySensor, ISamplingSensor<RelativeHumidity>, ISensor<RelativeHumidity>, ISensor, ISamplingSensor, II2cPeripheral

Inheritance: System.Object -> Meadow.Foundation.ObservableBase<UNIT>

Implements:

Expand

System.IObservable<Meadow.IChangeResult<System.ValueTuple<System.Nullable<Meadow.Units.Temperature>,System.Nullable<Meadow.Units.RelativeHumidity>>>>, Meadow.Peripherals.Sensors.ISamplingSensor<System.ValueTuple<System.Nullable<Meadow.Units.Temperature>,System.Nullable<Meadow.Units.RelativeHumidity>>>, Meadow.Peripherals.Sensors.ISensor<System.ValueTuple<System.Nullable<Meadow.Units.Temperature>,System.Nullable<Meadow.Units.RelativeHumidity>>>, System.IDisposable, Meadow.Peripherals.Sensors.ITemperatureSensor, Meadow.Peripherals.Sensors.ISamplingSensor<Meadow.Units.Temperature>, Meadow.Peripherals.Sensors.ISensor<Meadow.Units.Temperature>, Meadow.Peripherals.Sensors.Atmospheric.IHumiditySensor, Meadow.Peripherals.Sensors.ISamplingSensor<Meadow.Units.RelativeHumidity>, Meadow.Peripherals.Sensors.ISensor<Meadow.Units.RelativeHumidity>, Meadow.Peripherals.Sensors.ISensor, Meadow.Peripherals.Sensors.ISamplingSensor, Meadow.Hardware.II2cPeripheral

Properties

Temperature

The temperature from the last reading

View Source

Declaration

public Temperature? Temperature { get; }

Humidity

The humidity, in percent relative humidity, from the last reading

View Source

Declaration

public RelativeHumidity? Humidity { get; }

SerialNumber

Serial number of the device

View Source

Declaration

public ulong SerialNumber { get; }

SensorType

Device type as extracted from the serial number

View Source

Declaration

public Si70xx.DeviceType SensorType { get; }

FirmwareRevision

Firmware revision of the sensor

View Source

Declaration

public byte FirmwareRevision { get; }

DefaultI2cAddress

The default I2C address for the peripheral

View Source

Declaration

public byte DefaultI2cAddress { get; }

Methods

Reset()

Reset the sensor

View Source

Declaration

protected void Reset()

Initialize()

Initialize the sensor

View Source

Declaration

protected void Initialize()

ReadSensor()

Reads data from the sensor

View Source

Declaration

protected override Task<(Temperature? Temperature, RelativeHumidity? Humidity)> ReadSensor()

Returns

System.Threading.Tasks.Task<System.ValueTuple<System.Nullable<Meadow.Units.Temperature>,System.Nullable<Meadow.Units.RelativeHumidity>>>: The latest sensor reading### RaiseEventsAndNotify(IChangeResult<(Temperature? Temperature, RelativeHumidity? Humidity)>) Inheritance-safe way to raise events and notify observers.

View Source

Declaration

protected override void RaiseEventsAndNotify(IChangeResult<(Temperature? Temperature, RelativeHumidity? Humidity)> changeResult)

Parameters

Type	Name
Meadow.IChangeResult<System.ValueTuple<System.Nullable<Meadow.Units.Temperature>,System.Nullable<Meadow.Units.RelativeHumidity>>>	changeResult

Heater(bool)

Turn the heater on or off

View Source

Declaration

public void Heater(bool onOrOff)

Parameters

Type	Name	Description
System.Boolean	onOrOff	Heater status, true = turn heater on, false = turn heater off.

Implements

• System.IObservable<Meadow.IChangeResult<System.ValueTuple<System.Nullable<Meadow.Units.Temperature>,System.Nullable<Meadow.Units.RelativeHumidity>>>>
• Meadow.Peripherals.Sensors.ISamplingSensor<System.ValueTuple<System.Nullable<Meadow.Units.Temperature>,System.Nullable<Meadow.Units.RelativeHumidity>>>
• Meadow.Peripherals.Sensors.ISensor<System.ValueTuple<System.Nullable<Meadow.Units.Temperature>,System.Nullable<Meadow.Units.RelativeHumidity>>>
• System.IDisposable
• Meadow.Peripherals.Sensors.ITemperatureSensor
• Meadow.Peripherals.Sensors.ISamplingSensor<Meadow.Units.Temperature>
• Meadow.Peripherals.Sensors.ISensor<Meadow.Units.Temperature>
• Meadow.Peripherals.Sensors.Atmospheric.IHumiditySensor
• Meadow.Peripherals.Sensors.ISamplingSensor<Meadow.Units.RelativeHumidity>
• Meadow.Peripherals.Sensors.ISensor<Meadow.Units.RelativeHumidity>
• Meadow.Peripherals.Sensors.ISensor
• Meadow.Peripherals.Sensors.ISamplingSensor
• Meadow.Hardware.II2cPeripheral