.. highlight:: swift

Barometer
=========

Some MetaWear boards comes with a builtin barometer.  It's configured via properties on the `MBLBarometer <https://www.mbientlab.com/docs/metawear/ios/latest/Classes/MBLBarometer.html>`_ class.

To meet specific needs, different MetaWear models have different barometers, so the ``MBLBarometer`` class is actually a generic abstraction of all barometers.  You can up-cast to one of our derived barometer objects in order to access advanced features.

Pressure Reading
----------------

One thing common to all ambient light sensors is the ability to measure the ambient air pressure.

::

    device.barometer?.pressure.readAsync().success { result in
        print("pressure: \(result.value.doubleValue) pascals")
    }

Altitude Reading
----------------

Often times what you really want is an estimation of current altitude above sea level.  Since it's a complex non-linear function to get altitude from pressure, we have it built right in.

::

    device.barometer?.altitude.readAsync().success { result in
        print("altitude: \(result.value.doubleValue) meters")
    }

Cast to Derived Class
---------------------

To use advanced barometer features it's necessary to figure out exactly what barometer your MetaWear has.

::

    if let barometerBMP280 = device.barometer as? MBLBarometerBMP280 {
    }