Android GPS学习笔记—重要结构体及接口
gps.h文件中定义了GPS底层相关的结构体和接口。
目录：hardware/libhardware/include/hardware/gps.h
1. 相关宏定义
- 定位模式定义：GpsPositionMode
GPS定位模式分为：独立定位，MSB，MSA，其中独立定位表示只使用GPS芯片进行定位，MSB和MSA是AGPS定位的两种模式
<pre name="code" class="cpp">/** Requested operational mode for GPS operation. */ typedef uint32_t GpsPositionMode; // IMPORTANT: Note that the following values must match // constants in GpsLocationProvider.java. /** Mode for running GPS standalone (no assistance). */ #define GPS_POSITION_MODE_STANDALONE 0 /** AGPS MS-Based mode. */ #define GPS_POSITION_MODE_MS_BASED 1 /** AGPS MS-Assisted mode. */ #define GPS_POSITION_MODE_MS_ASSISTED 2
- GPS工作模式定义：GpsPositionRecurrence
GPS工作模式分为周期定位和单次定位
<pre name="code" class="cpp">/** Requested recurrence mode for GPS operation. */ typedef uint32_t GpsPositionRecurrence; // IMPORTANT: Note that the following values must match // constants in GpsLocationProvider.java. /** Receive GPS fixes on a recurring basis at a specified period. 周期性定位*/ #define GPS_POSITION_RECURRENCE_PERIODIC 0 /** Request a single shot GPS fix. 单次定位*/ #define GPS_POSITION_RECURRENCE_SINGLE 1
- GPS工作状态：GpsStatusValue
GPS工作状态分为：未知，正在定位，停止定位，启动未定义，未启动。
<pre name="code" class="cpp">/** GPS status event values. */ typedef uint16_t GpsStatusValue; // IMPORTANT: Note that the following values must match // constants in GpsLocationProvider.java. /** GPS status unknown. */ #define GPS_STATUS_NONE 0 /** GPS has begun navigating. */ #define GPS_STATUS_SESSION_BEGIN 1 /** GPS has stopped navigating. */ #define GPS_STATUS_SESSION_END 2 /** GPS has powered on but is not navigating. */ #define GPS_STATUS_ENGINE_ON 3 /** GPS is powered off. */ #define GPS_STATUS_ENGINE_OFF 4
- Location信息标志位
表明位置信息中哪些信息是可获得的
<pre name="code" class="cpp">/** 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. /** GpsLocation has valid latitude and longitude. */ #define GPS_LOCATION_HAS_LAT_LONG 0x0001 /** GpsLocation has valid altitude. */ #define GPS_LOCATION_HAS_ALTITUDE 0x0002 /** GpsLocation has valid speed. */ #define GPS_LOCATION_HAS_SPEED 0x0004 /** GpsLocation has valid bearing. */ #define GPS_LOCATION_HAS_BEARING 0x0008 /** GpsLocation has valid accuracy. */ #define GPS_LOCATION_HAS_ACCURACY 0x0010
- gps_set_capabilities 回调标志位
表示GPS芯片可以处理的能力
<pre name="code" class="cpp">/** Flags for the gps_set_capabilities callback. */
/** GPS HAL schedules fixes for GPS_POSITION_RECURRENCE_PERIODIC mode.
If this is not set, then the framework will use 1000ms for min_interval
and will start and call start() and stop() to schedule the GPS.
*/
#define GPS_CAPABILITY_SCHEDULING 0x0000001
/** GPS supports MS-Based AGPS mode */
#define GPS_CAPABILITY_MSB 0x0000002
/** GPS supports MS-Assisted AGPS mode */
#define GPS_CAPABILITY_MSA 0x0000004
/** GPS supports single-shot fixes */
#define GPS_CAPABILITY_SINGLE_SHOT 0x0000008
/** GPS supports on demand time injection */
#define GPS_CAPABILITY_ON_DEMAND_TIME 0x0000010
/** GPS supports Geofencing */
#define GPS_CAPABILITY_GEOFENCING 0x0000020
/** GPS supports Measurements */
#define GPS_CAPABILITY_MEASUREMENTS 0x0000040
/** GPS supports Navigation Messages */
#define GPS_CAPABILITY_NAV_MESSAGES 0x0000080
- 辅助数据
当调用函数delete_aiding_data()函数时用来区分删除哪种辅助数据
<pre name="code" class="cpp">/** Flags used to specify which aiding data to delete
when calling delete_aiding_data(). */
typedef uint16_t GpsAidingData;
// IMPORTANT: Note that the following values must match
// constants in GpsLocationProvider.java.
#define GPS_DELETE_EPHEMERIS 0x0001
#define GPS_DELETE_ALMANAC 0x0002
#define GPS_DELETE_POSITION 0x0004
#define GPS_DELETE_TIME 0x0008
#define GPS_DELETE_IONO 0x0010
#define GPS_DELETE_UTC 0x0020
#define GPS_DELETE_HEALTH 0x0040
#define GPS_DELETE_SVDIR 0x0080
#define GPS_DELETE_SVSTEER 0x0100
#define GPS_DELETE_SADATA 0x0200
#define GPS_DELETE_RTI 0x0400
#define GPS_DELETE_CELLDB_INFO 0x8000
#define GPS_DELETE_ALL 0xFFFF
- AGPS状态事件标志
<pre name="code" class="cpp">/** AGPS status event values. */ typedef uint16_t AGpsStatusValue; /** GPS requests data connection for AGPS. */ #define GPS_REQUEST_AGPS_DATA_CONN 1 /** GPS releases the AGPS data connection. */ #define GPS_RELEASE_AGPS_DATA_CONN 2 /** AGPS data connection initiated */ #define GPS_AGPS_DATA_CONNECTED 3 /** AGPS data connection completed */ #define GPS_AGPS_DATA_CONN_DONE 4 /** AGPS data connection failed */ #define GPS_AGPS_DATA_CONN_FAILED 5还有很多的宏定义在此不一一列举，在gps.h中有很好的解释。
2. 数据结构体
- GpsLocation
GPS位置信息的结构体，包含经纬度、高度、速度、方位角等
<pre name="code" class="cpp">/** Represents a location. */
typedef struct {
/** set to sizeof(GpsLocation) */
size_t size;
/** Contains GpsLocationFlags bits. */
uint16_t flags;
/** Represents latitude in degrees. */
double latitude;
/** Represents longitude in degrees. */
double longitude;
/** Represents altitude in meters above the WGS 84 reference
* ellipsoid. */
double altitude;
/** Represents speed in meters per second. */
float speed;
/** Represents heading in degrees. */
float bearing;
/** Represents expected accuracy in meters. */
float accuracy;
/** Timestamp for the location fix. */
GpsUtcTime timestamp;
} GpsLocation;
- GpsStatus
GPS工作状态分为：未知，正在定位，停止定位，启动未定义，未启动。（见前文宏定义）
<pre name="code" class="cpp">/** Represents the status. */
typedef struct {
/** set to sizeof(GpsStatus) */
size_t size;
GpsStatusValue status;
} GpsStatus;
- GpsSvInfo
表示当前的卫星信息：卫星编号，信号强度，仰望角，方位角
<pre name="code" class="cpp">/** Represents SV information. */
typedef struct {
/** set to sizeof(GpsSvInfo) */
size_t size;
/** Pseudo-random number for the SV. */
int prn;
/** Signal to noise ratio. */
float snr;
/** Elevation of SV in degrees. */
float elevation;
/** Azimuth of SV in degrees. */
float azimuth;
} GpsSvInfo;
- GpsSvStatus
表示卫星状态，包含了GpsSvInfo结构，可见卫星数，星历时间，年历时间，与用来定位的卫星构成的一个掩码
<pre name="code" class="cpp">/** Represents SV status. */
typedef struct {
/** set to sizeof(GpsSvStatus) */
size_t size;
/** Number of SVs currently visible. */
int num_svs;
/** Contains an array of SV information. */
GpsSvInfo sv_list[GPS_MAX_SVS];
/** Represents a bit mask indicating which SVs
* have ephemeris data.
*/
uint32_t ephemeris_mask;
/** Represents a bit mask indicating which SVs
* have almanac data.
*/
uint32_t almanac_mask;
/**
* Represents a bit mask indicating which SVs
* were used for computing the most recent position fix.
*/
uint32_t used_in_fix_mask;
} GpsSvStatus;
- AGpsRefLocation
定义AGPS相关的cell ID 和mac地址
<pre name="code" class="cpp">/* 2G and 3G */
/* In 3G lac is discarded */
typedef struct {
uint16_t type;
uint16_t mcc;
uint16_t mnc;
uint16_t lac;
uint32_t cid;
} AGpsRefLocationCellID;
typedef struct {
uint8_t mac[6];
} AGpsRefLocationMac;
/** Represents ref locations */
typedef struct {
uint16_t type;
union {
AGpsRefLocationCellID cellID;
AGpsRefLocationMac mac;
} u;
} AGpsRefLocation;
3. 回调函数指针定义
/** Callback with location information.告知上层位置信息 * Can only be called from a thread created by create_thread_cb. */ typedef void (* gps_location_callback)(GpsLocation* location); /** Callback with status information.GPS状态信息回调 * Can only be called from a thread created by create_thread_cb. */ typedef void (* gps_status_callback)(GpsStatus* status); /** * Callback with SV status information.卫星状态信息回调 * Can only be called from a thread created by create_thread_cb. */ typedef void (* gps_sv_status_callback)(GpsSvStatus* sv_info); /** Callback for reporting NMEA sentences.向上层传递NMEA信息 * Can only be called from a thread created by create_thread_cb. */ typedef void (* gps_nmea_callback)(GpsUtcTime timestamp, const char* nmea, int length); /** Callback to inform framework of the GPS engine's capabilities. * 告知上层GPS可以实现的功能 *Capability parameter is a bit field of GPS_CAPABILITY_* flags. */ typedef void (* gps_set_capabilities)(uint32_t capabilities); /** Callback utility for acquiring the GPS wakelock.GPS上锁，防止被suspend * This can be used to prevent the CPU from suspending while handling GPS events. */ typedef void (* gps_acquire_wakelock)(); /** Callback utility for releasing the GPS wakelock.释放锁 */ typedef void (* gps_release_wakelock)(); /** Callback for requesting NTP time 回调请求NTP时间*/ typedef void (* gps_request_utc_time)(); /** Callback for creating a thread that can call into the Java framework code. * 创建线程来响应framework层的请求 * This must be used to create any threads that report events up to the framework. */ typedef pthread_t (* gps_create_thread)(const char* name, void (*start)(void *), void* arg);
3. 接口结构体
- GpsCallbacks
就是上文函数指针组成的结构体，是一组回调函数，函数的实现在JNI层：com_android_server_location_GpsLocationProvider.cpp，GOOGLE已经实现好，无需做（太大）修改
/** GPS callback structure. */
typedef struct {
/** set to sizeof(GpsCallbacks) */
size_t size;
gps_location_callback location_cb;
gps_status_callback status_cb;
gps_sv_status_callback sv_status_cb;
gps_nmea_callback nmea_cb;
gps_set_capabilities set_capabilities_cb;
gps_acquire_wakelock acquire_wakelock_cb;
gps_release_wakelock release_wakelock_cb;
gps_create_thread create_thread_cb;
gps_request_utc_time request_utc_time_cb;
} GpsCallbacks;
- GpsInterface
GpsInterface接口是Android GPS 模块最重要的数据结构，它是底层驱动实现的接口，如果要porting到自己的板子上，就需要实现这些接口。
/** Represents the standard GPS interface. */
typedef struct {
/** set to sizeof(GpsInterface) */
size_t size;
/**
* Opens the interface and provides the callback routines
* to the implementation of this interface.
*/
int (*init)( GpsCallbacks* callbacks );
/** Starts navigating. 开始定位*/
int (*start)( void );
/** Stops navigating. 停止定位*/
int (*stop)( void );
/** Closes the interface. 关闭接口*/
void (*cleanup)( void );
/** Injects the current time. 注入当前时间*/
int (*inject_time)(GpsUtcTime time, int64_t timeReference,
int uncertainty);
/** Injects current location from another location provider
* (typically cell ID).注入位置信息
* latitude and longitude are measured in degrees
* expected accuracy is measured in meters
*/
int (*inject_location)(double latitude, double longitude, float accuracy);
/**
* Specifies that the next call to start will not use the
* information defined in the flags. GPS_DELETE_ALL is passed for
* a cold start.删除辅助数据
*/
void (*delete_aiding_data)(GpsAidingData flags);
/**
* min_interval represents the time between fixes in milliseconds.
* preferred_accuracy represents the requested fix accuracy in meters.
* preferred_time represents the requested time to first fix in milliseconds.
* 设置定位模式
*/
int (*set_position_mode)(GpsPositionMode mode, GpsPositionRecurrence recurrence,
uint32_t min_interval, uint32_t preferred_accuracy, uint32_t preferred_time);
/** Get a pointer to extension information. 自行添加接口实现*/
const void* (*get_extension)(const char* name);
} GpsInterface;
- GpsXtraCallbacks
高通XTRA加速定位技术回调函数结构体
<pre name="code" class="cpp">/** Callback structure for the XTRA interface. */
typedef struct {
gps_xtra_download_request download_request_cb;
gps_create_thread create_thread_cb;
} GpsXtraCallbacks;
- GpsXtraInterface
高通XTRA加速定位技术接口
/** Extended interface for XTRA support. */
typedef struct {
/** set to sizeof(GpsXtraInterface) */
size_t size;
/**
* Opens the XTRA interface and provides the callback routines
* to the implementation of this interface.
*/
int (*init)( GpsXtraCallbacks* callbacks );
/** Injects XTRA data into the GPS. */
int (*inject_xtra_data)( char* data, int length );
} GpsXtraInterface;
- AGpsInterface
AGPS加速定位技术接口结构体
<pre name="code" class="cpp">/** Extended interface for AGPS support. */
typedef struct {
/** set to sizeof(AGpsInterface_v1) */
size_t size;
/**
* Opens the AGPS interface and provides the callback routines
* to the implementation of this interface.
*/
void (*init)( AGpsCallbacks* callbacks );
/**
* Notifies that a data connection is available and sets
* the name of the APN to be used for SUPL.
*/
int (*data_conn_open)( const char* apn );
/**
* Notifies that the AGPS data connection has been closed.
*/
int (*data_conn_closed)();
/**
* Notifies that a data connection is not available for AGPS.
*/
int (*data_conn_failed)();
/**
* Sets the hostname and port for the AGPS server.
*/
int (*set_server)( AGpsType type, const char* hostname, int port );
} AGpsInterface;
- GpsNiInterface
网络端发起的定位接口结构体
/**
* Extended interface for Network-initiated (NI) support.
*/
typedef struct
{
/** set to sizeof(GpsNiInterface) */
size_t size;
/** Registers the callbacks for HAL to use. */
void (*init) (GpsNiCallbacks *callbacks);
/** Sends a response to HAL. */
void (*respond) (int notif_id, GpsUserResponseType user_response);
} GpsNiInterface;
- gps_device_t
定义描述GPS设备类型
struct gps_device_t {
struct hw_device_t common;
/**
* Set the provided lights to the provided values.
*
* Returns: 0 on succes, error code on failure.
*/
const GpsInterface* (*get_gps_interface)(struct gps_device_t* dev);
};
其他接口在此不再赘述。