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: