基于Android 的GPS 移植（主要结构体及接口介绍）

xiaoxiao2021-02-28 110

(http://blog.csdn.net/jwq2011/article/details/55268781)

最近负责 Android 驱动的GPS部分，所谓Android驱动我觉得可以说成是linux应用

之前发了一个图描述了 Android GPS 架构

GPS芯片大多采用串口通信，所以只要CPU能够提供一个UART 驱动，那么跟GPS芯片通信是没有问题的，

但是现在很多GPS功能不是一个单独的芯片，大部分都是一个芯片上有好几种无线模块比如 Blletooth WiFi FM等

有时候有些功能就会去复用一个UART，这样在管理上就相对麻烦，要将一个UART驱动，模拟成一个HCI的接口而后才能使GPS功能（TI1281）

比较好的是我们的项目是单一的GPS chip 听说apple也是用的这一款,不过人家拿的是全部的source code，而我们只有部分的code而没有核心算法的code 很郁闷，但是即便是只有部分code从里边还是可以学到很多的机制

对于android GPS驱动来说主要的工作是实现HAL层计编译生成一个叫做gps.***.so的动态库的代码. 由app发出定位申请，此时会去启动一个定位服务线程，此线程会调用到Location provider 服务在App Framwork中，在次会通过被native方法调用到JNI中，JNI获得GpsInterface并传给接口一个回调函数的实现。 GpsInterface就是由HAL层最主要实现介绍下gps.h下得重要相关结构题定义在android2.3中gps.h定义在/hardware/inclue/hardware下主要的结构 1、相关宏定义：

定位模式定义 /** 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 //纯GPS 使用卫星定位 /** AGPS MS-Based mode. */ #define GPS_POSITION_MODE_MS_BASED 1 //基于用户终端的A-GPS /** AGPS MS-Assisted mode. */ #define GPS_POSITION_MODE_MS_ASSISTED 2 //基于用户终端辅助A-GPS 工作模式 /** 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. */ #define GPS_POSITION_RECURRENCE_PERIODIC 0//周期性的 /** Request a single shot GPS fix. */ #define GPS_POSITION_RECURRENCE_SINGLE 1//单次工作辅助数据（在测试GPS性能时候又是需要删除全部或部分的辅助数据） /** 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 gps芯片可以处理的“能力” /** 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 还有很多的定义此处不一一列举在gps.h中都有很好的解释。

2、数据结构体

GpsLocation 定义了一个表示方位的结构体，成员有经纬度，高度，速度，方位角等。 GpsStatus 表示GPS的当前状态，只有两个成员一个是表示结构大小的成员，与一个表示Gps状态的类型GpsStatusValue /** 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 GpsSvInfo 表示当前的卫星信息，有卫星编号，信号强度，卫星仰望角方位角等 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，与用来定位的卫星的卫星构成的一个掩码 AGpsRefLocation /* 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; /** Represents the status of AGPS. */ typedef struct { /** set to sizeof(AGpsStatus) */ size_t size; AGpsType type; AGpsStatusValue status; } AGpsStatus

3、回调函数指针定义

/* Callback with location information. 告知上层位置信息*/ typedef void (* gps_location_callback)(GpsLocation* location); /** Callback with status information.GPS状态信息回调*/ typedef void (* gps_status_callback)(GpsStatus* status); /** Callback with SV status information.卫星状态信息回调 */ typedef void (* gps_sv_status_callback)(GpsSvStatus* sv_info); /** Callback for reporting NMEA sentences. 向上层传递NEMA数据*/ typedef void (* gps_nmea_callback)(GpsUtcTime timestamp, const char* nmea, int length); /** Callback to inform framework of the GPS engine's capabilities.告知上层次GPS能实现那些功能 */ typedef void (* gps_set_capabilities)(uint32_t capabilities); /** Callback utility for acquiring the GPS wakelock.gps上锁让gps功能不会被suspend*/ typedef void (* gps_acquire_wakelock)(); /** Callback utility for releasing the GPS wakelock. 释放锁*/ typedef void (* gps_release_wakelock)(); /** Callback for creating a thread that can call into the Java framework code.thread create 在次线程处理函数中通常会由一个无限的循环，去等待上层的请求，并应答*/ typedef pthread_t (* gps_create_thread)(const char* name, void (*start)(void *), void* arg);

4、接口结构体

GpsCallbacks 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; } GpsCallbacks；就是以上函数指针组成的结构体，是一组回调函数，函数的实现在JNI层是Android实现好了得，无需做（太大的）修改 GpsInterface Android GPS 最主要的数据结构，我们最主要的移植工作就是实现其中的函数 /** Represents the standard GPS interface. */ typedef struct { /** set to sizeof(GpsInterface) */ size_t size; /*Opens the interface and provides the callback routines 初始化callbacks 为JNI传下来的在此会使用callbacks中的create_thread_cb 来创建一个线程处理函数一直循环，等待任务处理*/ int (*init)( GpsCallbacks* callbacks ); /** Starts navigating. */ int (*start)( void ); /** Stops navigating. */ int (*stop)( void ); /** Closes the interface. */ void (*cleanup)( void ); /** Injects the current time. 填入时间*/ int (*inject_time)(GpsUtcTime time, int64_t timeReference, int uncertainty); /** Injects current location from another location provider 填入位置*/ int (*inject_location)(double latitude, double longitude, float accuracy); /*删除全部or部分辅助数据在性能测试时候使用*/ void (*delete_aiding_data)(GpsAidingData flags); /*设置定位模式与GPS工作模式等等*/ int (*set_position_mode)(GpsPositionMode mode, GpsPositionRecurrence recurrence, uint32_t min_interval, uint32_t preferred_accuracy, uint32_t preferred_time); /*自行添加的接口 AGpsInterface接口通过次函数获得*/ const void* (*get_extension)(const char* name); } GpsInterface; AGpsCallbacks /** Callback with AGPS status information. * Can only be called from a thread created by create_thread_cb. */ typedef void (* agps_status_callback)(AGpsStatus* status); /** Callback structure for the AGPS interface. */ typedef struct { agps_status_callback status_cb; gps_create_thread create_thread_cb; } AGpsCallbacks; AGpsInterface /** Extended interface for AGPS support. */ typedef struct { /** set to sizeof(AGpsInterface) */ size_t size; /** * Opens the AGPS interface and provides the callback routines * to the implemenation 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 struct 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); }; 上层会通过动态库，获得此结构，等到GpsInterface从而打通APP到GPS device的全部通信。

还有 GpsNiInterface AGpsRilInterface等接口在此不赘述文章转载至：http://www.linuxidc.com/Linux/2011-10/45371.htm，感谢作者的无私奉献！

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