Remarks
| 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:
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($"Observer: Temp changed by threshold; new temp: {result.New.Temperature?.Celsius:N2}C, old: {result.Old?.Temperature?.Celsius:N2}C");
},
filter: result =>
{
//c# 8 pattern match syntax. checks for !null and assigns var.
if (result.Old?.Temperature is { } oldTemp &&
result.Old?.Humidity is { } oldHumidity &&
result.New.Temperature is { } newTemp &&
result.New.Humidity is { } newHumidity)
{
return ((newTemp - oldTemp).Abs().Celsius > 0.5 &&
(newHumidity - oldHumidity).Percent > 0.05);
}
return false;
}
);
sensor.Subscribe(consumer);
sensor.Updated += (sender, result) =>
{
Resolver.Log.Info($" 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:
Syntax
public class Si70xx : ByteCommsSensorBase<(Units.Temperature? Temperature, RelativeHumidity? Humidity)>, ISamplingSensor<(Units.Temperature? Temperature, RelativeHumidity? Humidity)>, ISamplingSensor<(Units.Temperature? Temperature, RelativeHumidity? Humidity)>, IDisposable, ITemperatureSensor, IHumiditySensorConstructors
Si70xx(II2cBus, Byte)
Create a new SI7021 temperature and humidity sensor
Declaration
public Si70xx(II2cBus i2cBus, byte address = null)Parameters
| Type | Name | Description |
|---|---|---|
| II2cBus | i2cBus | I2CBus |
| System.Byte | address | I2C address (default to 0x40) |
Fields
DEFAULT_SPEED
Default SPI bus speed
Declaration
public static Frequency DEFAULT_SPEEDField Value
| Type | Description |
|---|---|
| Frequency |
Properties
FirmwareRevision
Firmware revision of the sensor
Declaration
public byte FirmwareRevision { get; }Property Value
| Type | Description |
|---|---|
| System.Byte |
Humidity
The humidity, in percent relative humidity, from the last reading
Declaration
public RelativeHumidity? Humidity { get; }Property Value
| Type | Description |
|---|---|
| System.Nullable<RelativeHumidity> |
SensorType
Device type as extracted from the serial number
Declaration
public Si70xx.DeviceType SensorType { get; }Property Value
| Type | Description |
|---|---|
| Si70xx.DeviceType |
SerialNumber
Serial number of the device
Declaration
public ulong SerialNumber { get; }Property Value
| Type | Description |
|---|---|
| System.UInt64 |
Temperature
The temperature, from the last reading
Declaration
public Units.Temperature? Temperature { get; }Property Value
| Type | Description |
|---|---|
| System.Nullable<Units.Temperature> |
Methods
Heater(Boolean)
Turn the heater on or off
Declaration
public void Heater(bool onOrOff)Parameters
| Type | Name | Description |
|---|---|---|
| System.Boolean | onOrOff | Heater status, true = turn heater on, false = turn heater off. |
Initialize()
Initalize the sensor
Declaration
protected void Initialize()RaiseEventsAndNotify(IChangeResult<(Nullable<Units.Temperature> Temperature, Nullable<RelativeHumidity> Humidity)>)
Inheritance-safe way to raise events and notify observers.
Declaration
protected override void RaiseEventsAndNotify(IChangeResult<(Units.Temperature? Temperature, RelativeHumidity? Humidity)> changeResult)Parameters
| Type | Name | Description |
|---|---|---|
| IChangeResult<System.ValueTuple<System.Nullable<Units.Temperature>, System.Nullable<RelativeHumidity>>> | changeResult |
ReadSensor()
Reads data from the sensor
Declaration
protected override Task<(Units.Temperature? Temperature, RelativeHumidity? Humidity)> ReadSensor()Returns
| Type | Description |
|---|---|
| Task<System.ValueTuple<System.Nullable<Units.Temperature>, System.Nullable<RelativeHumidity>>> | The latest sensor reading |
Overrides
Meadow.Foundation.SamplingSensorBase<System.ValueTuple<System.Nullable<Units.Temperature>, System.Nullable<RelativeHumidity>>>.ReadSensor()
Reset()
Reset the sensor
Declaration
protected void Reset()Events
HumidityUpdated
Raised when the humidity value changes
Declaration
public event EventHandler<IChangeResult<RelativeHumidity>> HumidityUpdatedEvent Type
| Type | Description |
|---|---|
| EventHandler<IChangeResult<RelativeHumidity>> |
TemperatureUpdated
Raised when the temperature value changes
Declaration
public event EventHandler<IChangeResult<Units.Temperature>> TemperatureUpdatedEvent Type
| Type | Description |
|---|---|
| EventHandler<IChangeResult<Units.Temperature>> |