Remarks

Bmp085
Status Status badge: working
Source code GitHub
Datasheet(s) GitHub
NuGet package NuGet Gallery for Meadow.Foundation.Sensors.Atmospheric.Bmp085

The BMP085 is a high-precision, low-power barometric pressure sensor. The BMP085 offers a measuring range of 300 to 1100 hPa with an absolute accuracy of down to 0.03 hPa. It's based on piezo-resistive technology for EMC robustness, high accuracy and linearity as well as long term stability. This sensor supports a voltage supply between 1.8 and 3.6VDC. It is designed to be connected directly to a micro-controller via the I2C bus.

Code Example

Bmp085? sensor;

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

    sensor = new Bmp085(Device.CreateI2cBus());

    var consumer = Bmp085.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.New.Temperature is { } newTemp)
            {
                return (newTemp - oldTemp).Abs().Celsius > 0.5; // returns true if > 0.5°C change.
            }
            return false;
        }
    );
    sensor.Subscribe(consumer);

    sensor.Updated += (sender, result) =>
    {
        Resolver.Log.Info($"  Temperature: {result.New.Temperature?.Celsius:N2}C");
        Resolver.Log.Info($"  Pressure: {result.New.Pressure?.Bar:N2}bar");
    };

    return Task.CompletedTask;
}

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

    var conditions = await sensor.Read();
    Resolver.Log.Info($"Temperature: {conditions.Temperature?.Celsius}°C, Pressure: {conditions.Pressure?.Pascal}Pa");

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

Sample project(s) available on GitHub

Wiring Example

To wire a BMP085 to your Meadow board, connect the following:

BMP085 Meadow Pin
GND GND
SCL D08 (SCL)
SDA D07 (SDA)
VCC 3V3

It should look like the following diagram:

Characteristic Locus
Inheritance System.Object > Bmp085
Implements ITemperatureSensor IBarometricPressureSensor
Namespace Meadow.Foundation.Sensors.Atmospheric
Assembly Bmp085.dll

Syntax

public class Bmp085 : ByteCommsSensorBase<(Units.Temperature? Temperature, Pressure? Pressure)>, ITemperatureSensor, IBarometricPressureSensor

Constructors

Bmp085(II2cBus, Byte, Bmp085.DeviceMode)

Create a new BMP085 object

Declaration
public Bmp085(II2cBus i2cBus, byte address = null, Bmp085.DeviceMode deviceMode = default(Bmp085.DeviceMode))

Parameters

Type Name Description
II2cBus i2cBus

The I2C bus

System.Byte address

The I2C address

Bmp085.DeviceMode deviceMode

The device mode

Properties

Pressure

Last value read from the Pressure sensor.

Declaration
public Pressure? Pressure { get; }

Property Value

Type Description
System.Nullable<Pressure>

Temperature

Last value read from the Pressure sensor.

Declaration
public Units.Temperature? Temperature { get; }

Property Value

Type Description
System.Nullable<Units.Temperature>

Methods

RaiseEventsAndNotify(IChangeResult<(Nullable<Units.Temperature> Temperature, Nullable<Pressure> Pressure)>)

Raise events for subcribers and notify of value changes

Declaration
protected override void RaiseEventsAndNotify(IChangeResult<(Units.Temperature? Temperature, Pressure? Pressure)> changeResult)

Parameters

Type Name Description
IChangeResult<System.ValueTuple<System.Nullable<Units.Temperature>, System.Nullable<Pressure>>> changeResult

The updated sensor data

ReadSensor()

Calculates the compensated pressure and temperature.

Declaration
protected override Task<(Units.Temperature? Temperature, Pressure? Pressure)> ReadSensor()

Returns

Type Description
Task<System.ValueTuple<System.Nullable<Units.Temperature>, System.Nullable<Pressure>>>

Events

PressureUpdated

Raised when the pressure value changes

Declaration
public event EventHandler<IChangeResult<Pressure>> PressureUpdated

Event Type

Type Description
EventHandler<IChangeResult<Pressure>>

TemperatureUpdated

Raised when the temperature value changes

Declaration
public event EventHandler<IChangeResult<Units.Temperature>> TemperatureUpdated

Event Type

Type Description
EventHandler<IChangeResult<Units.Temperature>>