Battery Service是有关电池特性方面的服务，如果需要它，在初始化时将它加入到蓝牙协议栈。
如果通过ble_bas_battery_level_update()，电池电量将会通知，Battery Service将发送事件到应用程序。
（1）Battery Service事件类型
/**@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事件处理函数
// 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);
（3）ble_bas_init_t：初始化用到的结构体
/**@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;
（4）包含可变状态信息的结构体ble_bas_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;
（5）几个函数说明：
uint32_t ble_bas_init (ble_bas_t *p_bas, const ble_bas_init_t *p_bas_init) //服务初始化 void ble_bas_on_ble_evt (ble_bas_t *p_bas, ble_evt_t *p_ble_evt) //处理协议栈事件的回调函数 uint32_t ble_bas_battery_level_update (ble_bas_t *p_bas, uint8_t battery_level) //更新电池电量时调用
（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 = ; err_code = ble_bas_init(&bas, &bas_init); APP_ERROR_CHECK(err_code);