About the relationship between API and events

[takashina hiroki]

SDK: 15.3.0
Example: ble_app_multirole_lesc
DeviceA: EYSHJNZWZ (nRF52832)

I want to know the relationship between API and events.
Take "sd_ble_gattc_characteristics_discover" as an example.

I expect to call “sd_ble_gattc_characteristics_discover” and get “BLE_GATTC_EVT_CHAR_DISC_RSP”.
Is there a case where "BLE_GATTC_EVT_CHAR_DISC_RSP" does not occur at this time?
Or does "BLE_GATTC_EVT_CHAR_DISC_RSP" always occur?
As a case where there is a possibility that "BLE_GATTC_EVT_CHAR_DISC_RSP" does not occur, we consider cases where there is no characteristic.

I gave "sd_ble_gattc_characteristics_discover" as an example, but I want to know the same for other APIs and events.
For example, “sd_ble_gattc_primary_services_discover” and “BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP”.

[0_velan_1]

HI here  (sd_ble_gattc_characteristics_discover(conn_range);

conn_range what parameter need to give...

if suppose through UART i am sending data like AT command format means

"AT+UBTGDCS=, <conn_parameter>,<start>,<end>" this data send through uart to sd_ble_gattc_characteristics_discover(); function how to get particular service charatertics  pelase help me?