AN4156

Sensor HAL: files

Doc ID 023584 Rev 1

5/12

2

Sensor HAL: files

In this section we examine the sensor HAL library files and its architecture model. There are

two configuration files in the library: configuration.h and sensors.h.

The configuration.h file is used to set some parameters such as the names of the

sensors, full scale defaults, names of the sysfs files, enable or disable debug information,

etc.

The sensors.h file is used to set the convert value of the data, the axis mapping through

rotation matrices and the event type of the drivers. The UML graph of the HAL library

structure is shown in Figure 4.

The library is written in C++ language using the object-oriented approach, for each sensor

there is a custom class file (AccelSensor.cpp, MagnSensor.cpp, GyroSensor.cpp

and PressTempSensor.cpp) which extends the common base class

(SensorBase.cpp).

2.1

Configuration.h

As mentioned above, the configuration file is used to describe some parameters of the

sensors. In this short paragraph we describe all the parameters and what they mean. An

example of a configuration file for the LSM303DLHC accelerometer is shown in Figure 2.

The first macro visible in this file, ANDROID_JELLY_BEAN, is used as the define if the

library is built for Android Jelly Bean version (4.1).

The parameters of the other sensors are the same as those used in this accelerometer

example.

..

...

/* ACCELEROMETER SENSOR \*/

#define SENSOR_ACC_LABEL

“LSM303DLHC 3-axis Accelerometer“

#define SENSOR_ACC_INCLUDE_FILE_NAME

“lsm303dlhc.h“

#define SENSOR_DATANAME_ACCELEROMETER

LSM303DLHC_ACC_DEV_NAME

#define ACCEL_DELAY_FILE_NAME

“pollrate_ms“

#define ACCEL_ENABLE_FILE_NAME

“enable_device”

#define ACCEL_RANGE_FILE_NAME

“range”

#define ACCEL_MAX_RANGE

16*GRAVITY_EARTH

#define ACCEL_MAX_ODR

400

#define ACCEL_POWER_CONSUMPTION

0.033f

#define ACCEL_DEFAULT_FULLSCALE

4

...

..

2.1.1

SENSOR_ACC_LABEL

This macro is used to define the sensor name visible in the Android application.