.. highlight:: csharp

Sensor Fusion
=============
Sensor fusion combines data from different sensors to compute something that cannot be calculated from one sensor alone.  MetaMotion boards run a Bosch 
sensor fusion algorithm that performs computations using BMI160 and BMM150 data in the firmware.  When using the sensor fusion algorithm, it is 
important that you do not simultaneously use the Accelerometer, Gyro, and Magnetometer modules.  Use the 
`ISensorFusionBosch <http://mbientlab.com/docs/metawear/csharp/1/interfaceMbientLab_1_1MetaWear_1_1Core_1_1ISensorFusionBosch.html>`_ interface to configure the 
algorithm which in turn will appropriately configure the required sensors.  ::

    using MbientLab.MetaWear.Core;

    ISensorFusionBosch sensorFusion = metawear.GetModule<ISensorFusionBosch>();

Configuration
-------------
There are 4 operation modes that use different combinations of the accelerometer, gyro, and magnetometer, enumerated by the 
`Mode <http://mbientlab.com/docs/metawear/csharp/1/namespaceMbientLab_1_1MetaWear_1_1Core_1_1SensorFusionBosch.html#aaf2f737a14477e3c2bcd1c7bee0ec2fe>`_ enum.  This, along with the data 
ranges for the accelerometer and gyroscope are set with the 
`Configure <http://mbientlab.com/docs/metawear/csharp/1/interfaceMbientLab_1_1MetaWear_1_1Core_1_1ISensorFusionBosch.html#aad18e6792c065c8196f1792704640d3b>`_ method.

======== ==========================================================================
Mode     Description                                                               
======== ==========================================================================
NDoF     Calculates absolute orientation from accelerometer, gyro, and magnetometer
IMUPlus  Calculates relative orientation in space from accelerometer and gyro data  
Compass  Determines geographic direction from th Earth's magnetic field            
M4G      Similar to IMUPlus except rotation is detected with the magnetometer      
======== ==========================================================================

The data rate and sensors used by the algorithm differ on based on the selected mode.

======== ===== ===== ====
Mode     Acc   Gyro  Mag
======== ===== ===== ====
NDoF     100Hz 100Hz 25Hz
IMUPlus  100Hz 100Hz N/A
Compass  25Hz  N/A   25Hz
M4G      50Hz  N/A   50Hz
======== ===== ===== ====

::

    using MbientLab.MetaWear.Core.SensorFusionBosch;

    // default settings is NDoF mode with +/-16g acc range and 2000dps gyro range
    sensorFusion.Configure();

Calibration
-----------
The IMU sensors will need some calibration in order to improve their accuracy.  After starting the sensor fusion algorithm, follow the calibration motions 
outlined in this Bosch tutorial video (`YouTube <https://www.youtube.com/watch?v=Bw0WuAyGsnY>`_).  

When the sensor fusion algorithm is calibrated, it will return the IMU calibration data.  The data can be written to the board after each power cycle to 
automatically calibrate the algorithm.  You can combine this with the :ref:`Macro` module to store the calibration in the flash memory.  ::

    // Use this token to cancel the calibration process
    var cts = new CancellationTokenSource();
    var data = await sensorFusion.Calibrate(cts.Token);

    // After a powr cycle, write the calibration data before configuring 
    // the sensor fusion algorithm
    sensorFusion.WriteCalibrationData(data);

Data
----
The algorithm can compute quaternion values and Euler angles as well as separating acceleration sources into linear motion and gravity.  Furthermore, 
it can use data from the other IMUs to correct the errors from the raw sensors.  Note that the units and type casting of the sensor fusion data is 
different for each type of data.

================ ======= ========================
Data             Units   Type 
================ ======= ========================
Acceleration     g       CorrectedAcceleration
Angular Velocity deg/s   CorrectedAngularVelocity 
Magnetic Field   T       CorrectedMagneticField
Quaternion       None    Quaternion
Euler Angles     degrees EulerAngles
Linear Acc       g       Acceleration
Gravity          g       Acceleration
================ ======= ========================

::

    using MbientLab.MetaWear.Data;

    // stream quaternion values from the board
    await sensorFusion.Quaternion.AddRouteAsync(source => 
        source.Stream(data => Console.WriteLine("Quaternion = " + data.Value<Quaternion>()))
    );