Battery Service是有關電池特性方面的服務，如果需要它，在初始化時將它加入到藍芽協議棧。

    如果通過ble_bas_battery_level_update()，電池電量將會通知，Battery Service將傳送事件到應用程式。

（1）Battery Service事件型別

/**@brief Battery Service event type. */
typedef enum
{
    BLE_BAS_EVT_NOTIFICATION_ENABLED,                             /**< Battery value notification enabled event. */
    BLE_BAS_EVT_NOTIFICATION_DISABLED                             /**< Battery value notification disabled event. */
} ble_bas_evt_type_t;

/**@brief Battery Service event. */
typedef struct
{
    ble_bas_evt_type_t evt_type;                                  /**< Type of event. */
} ble_bas_evt_t;
 

（2）Battery Service事件處理函式

// Forward declaration of the ble_bas_t type. 
typedef struct ble_bas_s ble_bas_t;

/**@brief Battery Service event handler type. */
typedef void (*ble_bas_evt_handler_t) (ble_bas_t * p_bas, ble_bas_evt_t * p_evt);

/**@brief Battery Service init structure. This contains all options and data needed for
 *        initialization of the service.*/
typedef struct
{
    ble_bas_evt_handler_t         evt_handler;                    /**< Event handler to be called for handling events in the Battery Service. */
    bool                          support_notification;           /**< TRUE if notification of Battery Level measurement is supported. */
    ble_srv_report_ref_t *        p_report_ref;                   /**< If not NULL, a Report Reference descriptor with the specified value will be added to the Battery Level characteristic */
    uint8_t                       initial_batt_level;             /**< Initial battery level */
    ble_srv_cccd_security_mode_t  battery_level_char_attr_md;     /**< Initial security level for battery characteristics attribute */
    ble_gap_conn_sec_mode_t       battery_level_report_read_perm; /**< Initial security level for battery report read attribute */
} ble_bas_init_t;
 

/**@brief Battery Service structure. This contains various status information for the service. */
typedef struct ble_bas_s
{
    ble_bas_evt_handler_t         evt_handler;                    /**< Event handler to be called for handling events in the Battery Service. */
    uint16_t                      service_handle;                 /**< Handle of Battery Service (as provided by the BLE stack). */
    ble_gatts_char_handles_t      battery_level_handles;          /**< Handles related to the Battery Level characteristic. */
    uint16_t                      report_ref_handle;              /**< Handle of the Report Reference descriptor. */
    uint8_t                       battery_level_last;             /**< Last Battery Level measurement passed to the Battery Service. */
    uint16_t                      conn_handle;                    /**< Handle of the current connection (as provided by the BLE stack, is BLE_CONN_HANDLE_INVALID if not in a connection). */
    bool                          is_notification_supported;      /**< TRUE if notification of Battery Level is supported. */
} ble_bas_t;
 

uint32_t  ble_bas_init (ble_bas_t *p_bas, const ble_bas_init_t *p_bas_init) //服務初始化
void  ble_bas_on_ble_evt (ble_bas_t *p_bas, ble_evt_t *p_ble_evt)  //處理協議棧事件的回撥函式
uint32_t  ble_bas_battery_level_update (ble_bas_t *p_bas, uint8_t battery_level) //更新電池電量時呼叫

（6）初始化操作

    // Here the sec level for the Battery Service can be changed/increased.
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&bas_init.battery_level_char_attr_md.cccd_write_perm);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&bas_init.battery_level_char_attr_md.read_perm);
    BLE_GAP_CONN_SEC_MODE_SET_NO_ACCESS(&bas_init.battery_level_char_attr_md.write_perm);

    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&bas_init.battery_level_report_read_perm);

    bas_init.evt_handler          = NULL;
    bas_init.support_notification = true;
    bas_init.p_report_ref         = NULL;
    bas_init.initial_batt_level   = 100;

    err_code = ble_bas_init(&bas, &bas_init);
    APP_ERROR_CHECK(err_code);