CC2541之回调函数代码解析

雨点打透心脏的1/2处 2022-06-11 05:45 311阅读 0赞

转自：香瓜博客

回调函数，解析代码：
    一 、定义一个 “ 成员为函数指针 ” 的结构体
    1 ）定义一个函数指针
    /**
    * Central Event Callback Function
    */
    typedef void (*pfnGapCentralRoleEventCB_t)
    (
    gapCentralRoleEvent_t *pEvent //!< Pointer to event structure.
    );
    它的参数是一个 gapCentralRoleEvent_t 类型的消息指针 *pEvent 。
    其中， gapCentralRoleEvent_t 的类型如下
    /**
    * Central Event Structure
    */
    typedef union
    {
    gapEventHdr_t gap; //!< GAP_MSG_EVENT and status.
    gapDeviceInitDoneEvent_t initDone; //!< GAP initialization done.
    gapDeviceInfoEvent_t deviceInfo; //!< Discovery device information event structure.
    gapDevDiscEvent_t discCmpl; //!< Discovery complete event structure.
    gapEstLinkReqEvent_t linkCmpl; //!< Link complete event structure.
    gapLinkUpdateEvent_t linkUpdate; //!< Link update event structure.
    gapTerminateLinkEvent_t linkTerminate; //!< Link terminated event structure.
    } gapCentralRoleEvent_t;
    2 ）定义一个结构体
    /**
    * Central Callback Structure
    */
    typedef struct
    {
    pfnGapCentralRoleRssiCB_t rssiCB; //!< RSSI callback.
    pfnGapCentralRoleEventCB_t eventCB; //!< Event callback.
    } gapCentralRoleCB_t;
    gapCentralRoleCB_t 结构体有两个成员，一个是 pfnGapCentralRoleRssiCB_t 类型的成员，一个是 pfnGapCentralRoleEventCB_t 类
    型的成员。
    二 、写一个回调函数，并完成注册
    1 ）定义一个函数 simpleBLECentralEventCB
    /*********************************************************************
    * @fn simpleBLECentralEventCB
    *
    * @brief Central event callback function.
    *
    * @param pEvent - pointer to event structure
    *
    * @return none
    */
    static void simpleBLECentralEventCB( gapCentralRoleEvent_t *pEvent )
    {
    switch ( pEvent->gap.opcode )
    {
    case GAP_DEVICE_INIT_DONE_EVENT:
    {
    LCD_WRITE_STRING( "BLE Central", HAL_LCD_LINE_1 );
    LCD_WRITE_STRING( bdAddr2Str( pEvent->initDone.devAddr ), HAL_LCD_LINE_2 );
    }
    break;
    case GAP_DEVICE_INFO_EVENT:
    {
    // if filtering device discovery results based on service UUID
    if ( DEFAULT_DEV_DISC_BY_SVC_UUID == TRUE )
    {
    if ( simpleBLEFindSvcUuid( SIMPLEPROFILE_SERV_UUID,
    pEvent->deviceInfo.pEvtData,
    pEvent->deviceInfo.dataLen ) )
    {
    simpleBLEAddDeviceInfo( pEvent->deviceInfo.addr, pEvent->deviceInfo.addrType );
    }
    }
    }
    break;
    case GAP_DEVICE_DISCOVERY_EVENT:
    {
    // discovery complete
    simpleBLEScanning = FALSE;
    // if not filtering device discovery results based on service UUID
    if ( DEFAULT_DEV_DISC_BY_SVC_UUID == FALSE )
    {
    // Copy results
    simpleBLEScanRes = pEvent->discCmpl.numDevs;
    osal_memcpy( simpleBLEDevList, pEvent->discCmpl.pDevList,
    (sizeof( gapDevRec_t ) * pEvent->discCmpl.numDevs) );
    }
    LCD_WRITE_STRING_VALUE( "Devices Found", simpleBLEScanRes,
    10, HAL_LCD_LINE_1 );
    if ( simpleBLEScanRes > 0 )
    {
    LCD_WRITE_STRING( "<- To Select", HAL_LCD_LINE_2 );
    }
    // initialize scan index to last device
    simpleBLEScanIdx = simpleBLEScanRes;
    }
    break;
    case GAP_LINK_ESTABLISHED_EVENT:
    {
    if ( pEvent->gap.hdr.status == SUCCESS )
    {
    simpleBLEState = BLE_STATE_CONNECTED;
    simpleBLEConnHandle = pEvent->linkCmpl.connectionHandle;
    simpleBLEProcedureInProgress = TRUE;
    // If service discovery not performed initiate service discovery
    if ( simpleBLECharHdl == 0 )
    {
    osal_start_timerEx( simpleBLETaskId, START_DISCOVERY_EVT, DEFAULT_SVC_DISCOVERY_DELAY );
    }
    LCD_WRITE_STRING( "Connected", HAL_LCD_LINE_1 );
    LCD_WRITE_STRING( bdAddr2Str( pEvent->linkCmpl.devAddr ), HAL_LCD_LINE_2 );
    }
    else
    {
    simpleBLEState = BLE_STATE_IDLE;
    simpleBLEConnHandle = GAP_CONNHANDLE_INIT;
    simpleBLERssi = FALSE;
    simpleBLEDiscState = BLE_DISC_STATE_IDLE;
    LCD_WRITE_STRING( "Connect Failed", HAL_LCD_LINE_1 );
    LCD_WRITE_STRING_VALUE( "Reason:", pEvent->gap.hdr.status, 10, HAL_LCD_LINE_2 );
    }
    }
    break;
    case GAP_LINK_TERMINATED_EVENT:
    {
    simpleBLEState = BLE_STATE_IDLE;
    simpleBLEConnHandle = GAP_CONNHANDLE_INIT;
    simpleBLERssi = FALSE;
    simpleBLEDiscState = BLE_DISC_STATE_IDLE;
    simpleBLECharHdl = 0;
    simpleBLEProcedureInProgress = FALSE;
    LCD_WRITE_STRING( "Disconnected", HAL_LCD_LINE_1 );
    LCD_WRITE_STRING_VALUE( "Reason:", pEvent->linkTerminate.reason,
    10, HAL_LCD_LINE_2 );
    }
    break;
    case GAP_LINK_PARAM_UPDATE_EVENT:
    {
    LCD_WRITE_STRING( "Param Update", HAL_LCD_LINE_1 );
    }
    break;
    default:
    break;
    }
    }
    2 ）声明函数
    static void simpleBLECentralEventCB( gapCentralRoleEvent_t *pEvent );
    3 ）使 simpleBLECentralEventCB 成为回调函数
    // GAP Role Callbacks
    static const gapCentralRoleCB_t simpleBLERoleCB =
    {
    simpleBLECentralRssiCB, // RSSI callback
    simpleBLECentralEventCB // Event callback
    };
    三 、调用回调函数
    1 ）定义一个新的函数指针变量 pGapCentralRoleCB （ central.c ）
    // App callbacks
    static gapCentralRoleCB_t *pGapCentralRoleCB;
    2 ）将 pGapCentralRoleCB 指向回调函数 simpleBLECentralEventCB ，也就是注册回调函数。
    /**
    * @brief Start the device in Central role. This function is typically
    * called once during system startup.
    *
    * Public function defined in central.h.
    */
    bStatus_t GAPCentralRole_StartDevice( gapCentralRoleCB_t *pAppCallbacks )
    {
    if ( pAppCallbacks )
    {
    pGapCentralRoleCB = pAppCallbacks;
    }
    return GAP_DeviceInit( gapCentralRoleTaskId, GAP_PROFILE_CENTRAL,
    gapCentralRoleMaxScanRes, gapCentralRoleIRK,
    gapCentralRoleSRK, &gapCentralRoleSignCounter );
    }
    3 ）调用回调函数
    // Pass event to app
    if ( pGapCentralRoleCB && pGapCentralRoleCB->eventCB )
    {
    pGapCentralRoleCB->eventCB( (gapCentralRoleEvent_t *) pMsg );
    }
    }
    注：实际上此时 simpleBLECentralEventCB 在第二步结束时，即可直接通过操作结构体来调用这个回调函数了。
    但是之所以要将结构体中的 simpleBLECentralEventCB 函数首地址再传给 simpleBLECentralEventCB （即第三点的 1 、 2 两个步骤）
    ，我认为是出于底层的 profiles——central 分层的考虑。