AWARE Accelerometer

The accelerometer measures the acceleration applied to the sensor built-in into the device, including the force of gravity. In other words, the force of gravity is always influencing the measured acceleration, thus when the device is sitting on a table, the accelerometer reads the acceleration of gravity: 9.81 m/s². Similarly, if the phone is in free-fall towards the ground, the accelerometer reads: 0 m/s².

The coordinate-system is defined relative to the screen of the phone in its default orientation (facing the user). The axis are not swapped when the device’s screen orientation changes. The X axis is horizontal and points to the right, the Y axis is vertical and points up and the Z axis points towards the outside of the front face of the screen. In this system, coordinates behind the screen have negative Z axis. Also, the natural orientation of a device is not always portrait, as the natural orientation for many tablet devices is landscape. For more information, check the official Android’s Sensor Coordinate System documentation.

Public functions

AccelerometerSensor

• start(context: Context, config: AccelerometerSensor.Config?): Starts the accelerometer sensor with the optional configuration.
• stop(context: Context): Stops the service.
• currentInterval: Data collection rate per second. (e.g. 5 samples per second)

AccelerometerSensor.Config

Class to hold the configuration of the sensor.

Fields

• sensorObserver: AccelerometerSensor.Observer: Callback for live data updates.
• interval: Int: Data samples to collect per second. (default = 5)
• period: Float: Period to save data in minutes. (default = 1)
• threshold: Double: If set, do not record consecutive points if change in value is less than the set value.
• enabled: Boolean Sensor is enabled or not. (default = false)
• debug: Boolean enable/disable logging to Logcat. (default = false)
• label: String Label for the data. (default = "")
• deviceId: String Id of the device that will be associated with the events and the sensor. (default = "")
• dbEncryptionKey Encryption key for the database. (default = null)
• dbType: Engine Which db engine to use for saving data. (default = Engine.DatabaseType.NONE)
• dbPath: String Path of the database. (default = "aware_accelerometer")
• dbHost: String Host for syncing the database. (default = null)

Broadcasts

Fired Broadcasts

• AccelerometerSensor.ACTION_AWARE_ACCELEROMETER fired when accelerometer saved data to db after the period ends.

Received Broadcasts

• AccelerometerSensor.ACTION_AWARE_ACCELEROMETER_START: received broadcast to start the sensor.
• AccelerometerSensor.ACTION_AWARE_ACCELEROMETER_STOP: received broadcast to stop the sensor.
• AccelerometerSensor.ACTION_AWARE_ACCELEROMETER_SYNC: received broadcast to send sync attempt to the host.
• AccelerometerSensor.ACTION_AWARE_ACCELEROMETER_SET_LABEL: received broadcast to set the data label. Label is expected in the AccelerometerSensor.EXTRA_LABEL field of the intent extras.

Data Representations

Accelerometer Sensor

Contains the hardware sensor capabilities in the mobile device.

Field	Type	Description
maxRange	Float	Maximum sensor value possible
minDelay	Float	Minimum sampling delay in microseconds
name	String	Sensor’s name
power	Float	Sensor’s power drain in mA
resolution	Float	Sensor’s resolution in sensor’s units
type	String	Sensor’s type
vendor	String	Sensor’s vendor
version	String	Sensor’s version
deviceId	String	AWARE device UUID
label	String	Customizable label. Useful for data calibration or traceability
timestamp	Long	unixtime milliseconds since 1970
timezone	Int	Raw timezone offset of the device
os	String	Operating system of the device (ex. android)

Accelerometer Data

Contains the raw sensor data.

Field	Type	Description
x	Float	the acceleration force along the x axis, including gravity, in m/s²
y	Float	the acceleration force along the y axis, including gravity, in m/s²
z	Float	the acceleration force along the z axis, including gravity, in m/s²
accuracy	Int	Sensor’s accuracy level (see SensorManager)
label	String	Customizable label. Useful for data calibration or traceability
deviceId	String	AWARE device UUID
label	String	Customizable label. Useful for data calibration or traceability
timestamp	Long	unixtime milliseconds since 1970
timezone	Int	Raw timezone offset of the device
os	String	Operating system of the device (ex. android)

Example usage

// To start the service.
AccelerometerSensor.start(appContext, AccelerometerSensor.Config().apply {
    sensorObserver = object : AccelerometerSensor.Observer {
        override fun onDataChanged(data: AccelerometerData) {
            // your code here...
        }
    }
    dbType = Engine.DatabaseType.ROOM
    debug = true
    // more configuration...
})

// To stop the service
AccelerometerSensor.stop(appContext)

License

Copyright (c) 2018 AWARE Mobile Context Instrumentation Middleware/Framework (http://www.awareframework.com)

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.