HAL之sensor

Sensor相关文件路径

（1）传感器系统的java部分，实现文件为sensor*.java
frameworks\base\core\java\android\hardware
（2）传感器系统等JNI部分，演示Android.hardware.Sensor.Manager类的本质支持
frameworks\base\core\jni\android_hardware_SensorManager.cpp
（3）传感器的HAL层，演示传感器系统的硬件抽象层需要具体的实现
hardware\libhardware\include\hardware\sensors.h
（4）驱动层，根据不同平台有所差异
kernel\drivers\hwmon$(PROJECT)\sensor

HAL层sensor代码

（1）文件的android.mk

LOCAL_MODULE := sensors.default  #重要，定义好的so名字，在JNI中会被加载调用LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/hwLOCAL_MODULE_TAGS := optionalLOCAL_CFLAGS := -DLOG_TAG=\"Sensors\" \-Wall \-DSENSORHAL_ACC_ADXL346#-DSENSORHAL_ACC_KXTF9LOCAL_SRC_FILES := \SensorBase.cpp \InputEventReader.cpp \AkmSensor.cpp \sensors.cpp \AdxlSensor.cppLOCAL_SHARED_LIBRARIES := liblog libcutils libdlLOCAL_PRELINK_MODULE := falseinclude $(BUILD_SHARED_LIBRARY)

（2）填充相关结构体–sensors.h中定义的

sensors_module_t 定义sensor模块

struct sensors_module_t {    struct hw_module_t common;    /**     * Enumerate all available sensors. The list is returned in "list".     * @return number of sensors in the list     */    int (*get_sensors_list)(struct sensors_module_t* module,            struct sensor_t const** list);};

其中get_sensors_list是用来获取sensor列表

sensor_t用来描述传感器信息

struct sensor_t {    const char*     name; //名称    const char*     vendor; //vendor？    int             version;//版本    int             handle;//句柄    int             type; //类型    float           maxRange; //最大范围    float           resolution;//解析度    float           power; //功耗    int32_t         minDelay;    uint32_t        fifoReservedEventCount;    uint32_t        fifoMaxEventCount;    void*           reserved[6];};

结构体和联合，sensor数据

/** * Union of the various types of sensor data * that can be returned. */typedef struct sensors_event_t {    /* must be sizeof(struct sensors_event_t) */    int32_t version;    /* sensor identifier */    int32_t sensor;    /* sensor type */    int32_t type;    /* reserved */    int32_t reserved0;    /* time is in nanosecond */    int64_t timestamp;    union {        union {            float           data[16];            /* acceleration values are in meter per second per second (m/s^2) */            sensors_vec_t   acceleration;            /* magnetic vector values are in micro-Tesla (uT) */            sensors_vec_t   magnetic;            /* orientation values are in degrees */            sensors_vec_t   orientation;            /* gyroscope values are in rad/s */            sensors_vec_t   gyro;            /* temperature is in degrees centigrade (Celsius) */            float           temperature;            /* distance in centimeters */            float           distance;            /* light in SI lux units */            float           light;            /* pressure in hectopascal (hPa) */            float           pressure;            /* relative humidity in percent */            float           relative_humidity;           /* uncalibrated gyroscope values are in rad/s */            uncalibrated_event_t uncalibrated_gyro;            /* uncalibrated magnetometer values are in micro-Teslas */            uncalibrated_event_t uncalibrated_magnetic;            /* this is a special event. see SENSOR_TYPE_META_DATA above.             * sensors_meta_data_event_t events are all reported with a type of             * SENSOR_TYPE_META_DATA. The handle is ignored and must be zero.             */            meta_data_event_t meta_data;        };        union {            uint64_t        data[8];            /* step-counter */            uint64_t        step_counter;        } u64;    };    uint32_t reserved1[4];} sensors_event_t;

（3）适配层函数接口

/** convenience API for opening and closing a device */static inline int sensors_open(const struct hw_module_t* module,        struct sensors_poll_device_t** device) {    return module->methods->open(module,            SENSORS_HARDWARE_POLL, (struct hw_device_t**)device);}static inline int sensors_close(struct sensors_poll_device_t* device) {    return device->common.close(&device->common);}static inline int sensors_open_1(const struct hw_module_t* module,        sensors_poll_device_1_t** device) {    return module->methods->open(module,            SENSORS_HARDWARE_POLL, (struct hw_device_t**)device);}static inline int sensors_close_1(sensors_poll_device_1_t* device) {    return device->common.close(&device->common);

在驱动提供的代码要实现file_operations。

sensor编程的流程

（1）获取系统服务，返回一个SensorManager对象
sensormanager = (SensorManager)getSystemServer(SENSOR_SERVICE);
（2）通过SensorManager对象获取相应的Sensor类型对象
sensorObject = sensormanager.getDefaultSesor(Sensor Type);
（3）声明一个SensorEventListener对象检测Sensor事件，重载onSensorChanged方法
SensorEventListener = new SensorEventListener(){ };
（4）注册相应的SensorService
sensormanager.registerListener(sensorListener, sensorObject, Sensor type);
（5）销毁SensorService
sensormanager.registerListener(sensorListener, sensorObject);

SensorListener接口是整个传感器应用程序的核心，包含如下两个必须的方法：
onSensorChange(int sensor, float values[]):此方法在传感器值更改时调用，该方法只对受此应用程序监视的传感器调用（）。该方法包含两个参数：
1、一个整数：指出更改的传感器是哪个
2、一个浮点值数组：表示传感器数据
onAccuracyChanged(int sensor, int accuracy):当传感器的准确值更新时调用此函数。

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