Read environmental conditions from a sensor

One of the most common scenarios for IoT devices is detection of environmental conditions. A variety of sensors are available to monitor temperature, humidity, barometric pressure, and more.

In this topic, you will use .NET to read environmental conditions from a sensor.

Prerequisites

• ARM-based (ARMv7 or greater) single-board computer (SBC)
• BME280 humidity/barometric pressure/temperature sensor breakout
• Jumper wires
• Breadboard (optional)
• Raspberry Pi GPIO breakout board (optional)
• .NET SDK 7 or later

Prepare the SBC

Ensure your SBC is configured to support the following services:

• SSH
• I2C

For many devices, no additional configuration is required. For Raspberry Pi, use the raspi-config command. For more information on raspi-config, refer to the Raspberry Pi documentation.

Prepare the hardware

Use the hardware components to build the circuit as depicted in the following diagram:

The following are the connections from the Raspberry Pi to the BME280 breakout. Note that pin labels differ on various BME280 breakouts.

Refer to the following pinout diagram as needed:

Image courtesy Raspberry Pi Foundation.

Create the app

Complete the following steps in your preferred development environment:

1. Create a new .NET Console App using either the .NET CLI or Visual Studio. Name it SensorTutorial.

   dotnet new console -o SensorTutorial
   cd SensorTutorial
   

2. Add the Iot.Device.Bindings package to the project. Use either .NET CLI from the project directory or Visual Studio.

   dotnet add package Iot.Device.Bindings --version 2.2.0-*
   

3. Replace the contents of Program.cs with the following code:

   using System;
   using System.Device.I2c;
   using System.Threading;
   using Iot.Device.Bmxx80;
   using Iot.Device.Bmxx80.PowerMode;
   
   var i2cSettings = new I2cConnectionSettings(1, Bme280.DefaultI2cAddress);
   using I2cDevice i2cDevice = I2cDevice.Create(i2cSettings);
   using var bme280 = new Bme280(i2cDevice);
   
   int measurementTime = bme280.GetMeasurementDuration();
   
   while (true)
   {
       Console.Clear();
   
       bme280.SetPowerMode(Bmx280PowerMode.Forced);
       Thread.Sleep(measurementTime);
   
       bme280.TryReadTemperature(out var tempValue);
       bme280.TryReadPressure(out var preValue);
       bme280.TryReadHumidity(out var humValue);
       bme280.TryReadAltitude(out var altValue);
   
       Console.WriteLine($"Temperature: {tempValue.DegreesCelsius:0.#}\u00B0C");
       Console.WriteLine($"Pressure: {preValue.Hectopascals:#.##} hPa");
       Console.WriteLine($"Relative humidity: {humValue.Percent:#.##}%");
       Console.WriteLine($"Estimated altitude: {altValue.Meters:#} m");
   
       Thread.Sleep(1000);
   }
   

   In the preceding code:

   • i2cSettings is set to a new instance of I2cConnectionSettings. The constructor sets the busId parameter to 1 and the deviceAddress parameter to Bme280.DefaultI2cAddress.

     Important

     Some BME280 breakout manufacturers use the secondary address value. For those devices, use Bme280.SecondaryI2cAddress.

   • A using declaration creates an instance of I2cDevice by calling I2cDevice.Create and passing in i2cSettings. This I2cDevice represents the I²C bus. The using declaration ensures the object is disposed and hardware resources are released properly.

   • Another using declaration creates an instance of Bme280 to represent the sensor. The I2cDevice is passed in the constructor.

   • The time required for the chip to take measurements with the chip's current (default) settings is retrieved by calling GetMeasurementDuration.

   • A while loop runs indefinitely. Each iteration:

     1. Clears the console.

     2. Sets the power mode to Bmx280PowerMode.Forced. This forces the chip to perform one measurement, store the results, and then sleep.

     3. Reads the values for temperature, pressure, humidity, and altitude.

        Note

        Altitude is calculated by the device binding. This overload of TryReadAltitude uses mean sea level pressure to generate an estimate.

     4. Writes the current environmental conditions to the console.

     5. Sleeps 1000 ms.

4. Build the app. If using the .NET CLI, run dotnet build. To build in Visual Studio, press Ctrl+Shift+B.

5. Deploy the app to the SBC as a self-contained app. For instructions, see Deploy .NET apps to Raspberry Pi. Make sure to give the executable execute permission using chmod +x.

6. Run the app on the Raspberry Pi by switching to the deployment directory and running the executable.

   ./SensorTutorial
   

   Observe the sensor output in the console.

7. Terminate the program by pressing Ctrl+C.

Congratulations! You've used I²C to read values from a temperature/humidity/barometric pressure sensor!

Get the source code

The source for this tutorial is available on GitHub.

Next steps