how to initialize event handler??

[renu]

Hi all, i am doing a BLE project using nrf51822 hardware, in this project my requirement is to initialize the event, for doing that i took ble_app_proximity,ble_app_hrs as reference code ,

  so what i did to meet my requirement is ,
  from main() i called services_init()
  and in this i intialize 
  ble_hrs_init_t->evt_handler=evt_handler;[refered from ble_app_hrs ]
  and my evt_handlert defination is like this 
  evt_handler(ble_hrs_t *p_nus,  ble_hrs_evt_t * p_evt)
  it seems there is two type of structure related  to evnt
  1)typedef struct
	{
		ble_hrs_evt_type_t evt_type;                        /**< Type of event. */
	} ble_hrs_evt_t;
 2)typedef struct
	{
		ble_evt_hdr_t header;                 /**< Event header. */
		union
		{
			ble_common_evt_t  common_evt;         /**< Common Event, evt_id in BLE_EVT_* series. */
			ble_gap_evt_t     gap_evt;            /**< GAP originated event, evt_id in BLE_GAP_EVT_* series. */
			ble_l2cap_evt_t   l2cap_evt;          /**< L2CAP originated event, evt_id in BLE_L2CAP_EVT* series. */
			ble_gattc_evt_t   gattc_evt;          /**< GATT client originated event, evt_id in BLE_GATTC_EVT* series. */
			ble_gatts_evt_t   gatts_evt;          /**< GATT server originated event, evt_id in BLE_GATTS_EVT* series. */
		} evt;
	} ble_evt_t;
  so my doubt is:
  1) which data structure should use as second pararameter of  evt_handler either ble_hrs_evt_t or ble_evt_t?
  2)if i use  ble_hrs_evt_t as second parameter, then this has member  ble_hrs_evt_type_t which is enum of this type
  typedef enum
 {
   BLE_HRS_EVT_NOTIFICATION_ENABLED,                   /**< Heart Rate value notification enabled event. */
   BLE_HRS_EVT_NOTIFICATION_DISABLED                   /**< Heart Rate value notification disabled event. */
 } ble_hrs_evt_type_t;
 so in this can i define my own event type?
     3) under what situations is one data structure preferred over other, for example in ble_hrs ble_hrs_evt_t; is used 
     4) under ble_app_proximity project, the ble_evt_t is used and i wanted to know the reason behind using this structure as compared to 
         point 3.

Can any one please share information related to this....? Thanks Renu

[FormerMember]

1. The second parameter of the event handler should be ble_evt_t. When receiving a BLE event, it is in the format of ble_evt_t.
2. When receiving an event, ble_evt_t should used, see 1. As you can see in ble_hrs.c, ble_hrs_evt_t is used to "process" a received event in on_hrm_cccd_write(..). on_hrm_cccd_write is called in on_write, and on_write(..)receives the BLE event in the format of ble_evt_t.

Edit:

ble_app_proximity: the purpose of the event handler on_ias_evt is to handle immediate alert service events. BLE_IAS_EVT_ALERT_LEVEL_UPDATED-is passed to the application from ble_evt_dispatch(..) --> ble_ias_on_ble_evt(..) --> on_write(..) --> p_ias->evt_handler(..):

 static void on_write(ble_ias_t * p_ias, ble_evt_t * p_ble_evt)
{
    ble_gatts_evt_write_t * p_evt_write = &p_ble_evt->evt.gatts_evt.params.write;

    if ((p_evt_write->handle == p_ias->alert_level_handles.value_handle) && (p_evt_write->len == 1))
    {
        // Alert level written, call application event handler
        ble_ias_evt_t evt;

        evt.evt_type           = BLE_IAS_EVT_ALERT_LEVEL_UPDATED;
        evt.params.alert_level = p_evt_write->data[0];

        p_ias->evt_handler(p_ias, &evt);
    }
} 

ble_app_hrs is built the same way: ble_evt_dispatch(..) --> ble_hrs_on_ble_evt(..) --> on_write(..) --> on_hrm_cccd_write(..) . However, there are no events associated with notifications enabled or disabled. And therefore, it is no need for an event handler, so the event handler that is called is null:

static void on_hrm_cccd_write(ble_hrs_t * p_hrs, ble_gatts_evt_write_t * p_evt_write)
{
    if (p_evt_write->len == 2)
    {
        // CCCD written, update notification state
        if (p_hrs->evt_handler != NULL)
        {
            ble_hrs_evt_t evt;

            if (ble_srv_is_notification_enabled(p_evt_write->data))
            {
                evt.evt_type = BLE_HRS_EVT_NOTIFICATION_ENABLED;
            }
            else
            {
                evt.evt_type = BLE_HRS_EVT_NOTIFICATION_DISABLED;
            }

            p_hrs->evt_handler(p_hrs, &evt);
        }
    }
}

The purpose of softdevice_sys_evt_handler_set(..) is to register system events from the softDevice, see its documentation here.

The purpose of softdevice_ble_evt_handler_set(..)is to register a handler for BLE events, see its documentation here.

[renu]

thanks for replying Kristin