Sensor Data Streaming

Control Sensors and Acquire Data

This example shows a simple workflow of controlling mobile device sensors and acquiring data from them.

This example assumes that you have already installed and set up MATLAB^® Mobile™ on your mobile device and connected it to the MathWorks Cloud. If you have not, see Install MATLAB Mobile on Your Device.

Start MATLAB Mobile on your mobile device.
Sign in to the Cloud, if prompted.
On the Sensors screen, turn on the sensors that you want to send data from using the toggle switches.
In the sensor settings, tap Stream to and then select MATLAB.
Place the device where you want to acquire the sensor data.
In MATLAB, create a mobiledev object, m.
```
m = mobiledev
```
```
m = 
mobiledev with properties:

                   Connected: 1
           Available Cameras: {'back' 'front'}
                     Logging: 0
            InitialTimestamp: ''

   AccelerationSensorEnabled: 1
AngularVelocitySensorEnabled: 1
       MagneticSensorEnabled: 1
    OrientationSensorEnabled: 1
       PositionSensorEnabled: 1

Supported functions
```
In the display, a value of 1 means enabled or on, and 0 means not enabled or off. In this example, you can see that the device and the Cloud are connected, and all the sensors are enabled (from the Sensors screen), but data is not being logged yet. This device contains all five sensors, but your device might not. If your device does not have a particular sensor, that sensor always show a 0 in the display. The timestamp is empty because no data has been logged yet.
InitialTimestamp is the timestamp of the first data point received by mobiledev. All other timestamps for all sensors are relative to InitialTimestamp.
Begin logging data from the selected sensors by setting the Logging property.
```
m.Logging = 1
```
This action starts the transmission of data from all selected sensors. You can also start transmission by tapping the Start button in MATLAB Mobile on the device.

Now that you have started logging data, view the mobiledev object with the disp function.

disp(m)

mobiledev with properties:

                   Connected: 1
           Available Cameras: {'back' 'front'}
                     Logging: 1
            InitialTimestamp: '06-08-2014 13:45:56.529'

   AccelerationSensorEnabled: 1
AngularVelocitySensorEnabled: 1
       MagneticSensorEnabled: 1
    OrientationSensorEnabled: 1
       PositionSensorEnabled: 1

Current Sensor Values:
                Acceleration: [0.27 0.23 -10.19]  (m/s^2)
             AngularVelocity: [-0.22 0.07 0.06]   (rad/s)
               MagneticField: [3.56 1.56 -48.19]  (microtesla)
                 Orientation: [85.91 -27.1 0.35]  (degrees)

       Position Data: 
                    Latitude: 41.29  (degrees)
                   Longitude: -72.35  (degrees)
                       Speed: 25  (m/s)
                      Course: 83.6  (degrees)
                    Altitude: 200.1  (m)
          HorizontalAccuracy: 9.0  (m)
                                                                 
Supported functions

In this display, you can see that the device and the Cloud are connected, and data is now being logged. You can also now see the InitialTimestamp property value, and the sensor values are displayed, indicating the current measurement value when you created the object.

While you are logging data, you can display the current value of any sensor using the sensor reading properties. The Acceleration, AngularVelocity, Orientation, and MagneticField properties display the current readings from their respective sensors. If the Position sensor is logging, you can get individual position readings using the Latitude, Longitude, HorizontalAccuracy, Altitude, Course, and Speed properties.
For example, to get the Acceleration sensor reading for object m:
```
m.Acceleration
```
```
ans =

    0.6945   -0.2579    9.9338
```
To get the longitude reading from the Position sensor:
```
m.Longitude
```
```
ans =

    -71.3517
```
You can turn the sensors on and off using the sensor control properties in MATLAB. Using the control properties is the same as toggling the sensor buttons in MATLAB Mobile. Each control property has two possible values: 1 for on or enabled, and 0 for off or disabled. For example, to turn off the Acceleration sensor from MATLAB:
```
m.AccelerationSensorEnabled = 0
```
To turn back on the Acceleration sensor:
```
m.AccelerationSensorEnabled = 1
```
Stop logging sensor data.
```
m.Logging = 0
```
You can use the sensor reading properties to get the current value of a sensor while you are logging data, as shown in step 7. If you want to see the entire log of all readings, use the log functions. You can use these functions while you are still logging data, or after you stop. Each sensor type has a log function, for example, accellog returns the logged acceleration data from the Acceleration sensor.
To get the logged acceleration data from object m, assign the variable a for the logged acceleration data and t for the timestamps.
```
[a, t] = accellog(m);
```
You can then plot the data or do other data processing.
When you are done with the session, delete the object.
```
clear m
```

Sensor Data Streaming

Control Sensors and Acquire Data

See Also

Topics