Best items pulled from Android's sensors.h and gps.h definitions to aid in common sensor data definitions

android_sensor_gps.h

/*** How Android does GPS ***/
/* Source at https://github.com/android/platform_hardware_libhardware/blob/master/include/hardware/gps.h */


typedef int64_t GpsUtcTime; /** Milliseconds since January 1, 1970 */

/** Flags to indicate which values are valid in a GpsLocation. */
typedef uint16_t GpsLocationFlags;
// IMPORTANT: Note that the following values must match
// constants in GpsLocationProvider.java.
#define GPS_LOCATION_HAS_LAT_LONG   0x0001
#define GPS_LOCATION_HAS_ALTITUDE   0x0002
#define GPS_LOCATION_HAS_SPEED      0x0004
#define GPS_LOCATION_HAS_BEARING    0x0008
#define GPS_LOCATION_HAS_ACCURACY   0x0010


/** Represents a location. */
typedef struct {  
    size_t      size; /** set to sizeof(GpsLocation) */
    uint16_t    flags; /** Contains GpsLocationFlags bits. */
    double      latitude; /** Latitude in degrees. */
    double      longitude; /** Longitude in degrees. */
    double      altitude; /* altitude in meters above the WGS 84 ellipsoid */
    float       speed; /**  speed in meters per second. */
    float       bearing; /** heading in degrees. */
    float       accuracy; /**  expected accuracy in meters. */
    GpsUtcTime  timestamp; /** Timestamp for the location fix. */
} GpsLocation;

/*** Rest of file is how Android does sensors ***/
/* Source at https://github.com/android/platform_hardware_libhardware/blob/master/include/hardware/sensors.h */

/* SENSOR_TYPE_META_DATA */

#define SENSOR_TYPE_DEVICE_PRIVATE_BASE     0x10000 /* Base for device manufacturers private sensor types. Cannot be exposed in the SDK. */
#define SENSOR_TYPE_META_DATA (0) /* special token used to populate the sensors_meta_data_event structure. */
#define SENSOR_TYPE_ACCELEROMETER (1)  /* Acceleration in x, y, z axis in m/s^s */
#define SENSOR_TYPE_GEOMAGNETIC_FIELD (2) /* Mag field in micro Tesla (uT) in x, y, z axis  */.
#define SENSOR_TYPE_MAGNETIC_FIELD  SENSOR_TYPE_GEOMAGNETIC_FIELD
#define SENSOR_TYPE_ORIENTATION (3) /* Azimuth, pitch and roll in degrees */ 
#define SENSOR_TYPE_GYROSCOPE (4) /* Rotation in rad/sec around x, y, z */
#define SENSOR_TYPE_LIGHT (5) /* The light sensor value is returned in SI lux units. */
#define SENSOR_TYPE_PRESSURE (6) /* The pressure sensor return the athmospheric pressure in hectopascal (hPa) */
#define SENSOR_TYPE_TEMPERATURE (7) /* Deprecated in Android */
#define SENSOR_TYPE_PROXIMITY (8) /* The distance value is measured in centimeters */
#define SENSOR_TYPE_GRAVITY (9) /* Gravity in x, y and z in m/s^s relative to sensor */
#define SENSOR_TYPE_LINEAR_ACCELERATION (10) /* m/s^2 * The coordinate system is the same used for the accelerometer */
#define SENSOR_TYPE_ROTATION_VECTOR (11) /** **/
#define SENSOR_TYPE_RELATIVE_HUMIDITY (12) /* relative ambient air humidity as a value in percent */
#define SENSOR_TYPE_AMBIENT_TEMPERATURE (13) /* The ambient (room) temperature in degree Celsius. */
#define SENSOR_TYPE_MAGNETIC_FIELD_UNCALIBRATED  (14) /* See SENSOR_TYPE_GEOMAGNETIC_FIELD */
#define SENSOR_TYPE_GAME_ROTATION_VECTOR (15) /* Similar SENSOR_TYPE_ROTATION_VECTOR but without magnetic north */
#define SENSOR_TYPE_GYROSCOPE_UNCALIBRATED (16) /* Rotation in rad/sec around x, y, z */
#define SENSOR_TYPE_SIGNIFICANT_MOTION (17) /* Only value is 1.0, indicates significant motion event */
#define SENSOR_TYPE_STEP_DETECTOR (18) /* Triggers an event each time a step is taken, returning a value of 1.0 */
#define SENSOR_TYPE_STEP_COUNTER (19) /* Number of steps taken by the user since the last reboot while activated */
#define SENSOR_TYPE_GEOMAGNETIC_ROTATION_VECTOR (20) /* see SENSOR_TYPE_ROTATION_VECTOR for more details */



struct sensor_t {
    const char*     name; /* Name of this sensor. All of same "type" must have a different "name". */
    const char*     vendor; /* vendor of the hardware part */    
    int             version;  /* Firmware version */
    int             handle;  /* Essentially the sensor ID*/
    int             type; /* See types */
    float           maxRange; /* M maximum range of this sensor's value in SI units */
    float           resolution; /* smallest difference between two values reported by this sensor */
    float           power;   /* rough estimate of this sensor's power consumption in mA */
    int32_t         minDelay; /* Default is 0 (on-change), -1 = on-shot, otherwise microseconds between reads */
    uint32_t        fifoReservedEventCount; /* number of events reserved for this sensor in the batch mode FIFO. */
    uint32_t        fifoMaxEventCount; /* maximum number of events of this sensor that could be batched. */
    void*           reserved[6]; /* reserved fields, must be zero */
};


/*** status of orientation sensor */

#define SENSOR_STATUS_UNRELIABLE        0
#define SENSOR_STATUS_ACCURACY_LOW      1
#define SENSOR_STATUS_ACCURACY_MEDIUM   2
#define SENSOR_STATUS_ACCURACY_HIGH     3




/************** sensor event data applicable to most sensors ********/

typedef struct {
    union {
        float v[3];
        struct {
            float x;
            float y;
            float z;
        };
        struct {
            float azimuth;
            float pitch;
            float roll;
        };
    };
    int8_t status;
    uint8_t reserved[3];
} sensors_vec_t;

/************** uncalibrated gyroscope and magnetometer event data ********/
typedef struct {
  union {
    float uncalib[3];
    struct {
      float x_uncalib;
      float y_uncalib;
      float z_uncalib;
    };
  };
  union {
    float bias[3];
    struct {
      float x_bias;
      float y_bias;
      float z_bias;
    };
  };
} uncalibrated_event_t;


/*** Meta-data event for a sensor - e.g., Tamper */
typedef struct meta_data_event {
    int32_t what;
    int32_t sensor;
} meta_data_event_t;


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