central side:
initiate connection with CA A4 F4 EA DE 1B
sd_ble_gap_connect

[DM]: Request to allocation connection instance
[DM]:[00]: Connection Instance Allocated.
[DM]: Searching for device 0x1B 0xDE 0xEA 0xF4 0xA4 0xCA.
[DM]:[DI 0x00]: Device type 0xFF.
[DM]: Device Addr 0x00 0x00 0x00 0x00 0x00 0x00.
[DM]:[DI 0x01]: Device type 0xFF.
[DM]: Device Addr 0x00 0x00 0x00 0x00 0x00 0x00.
[DM]:[DI 0x02]: Device type 0xFF.
[DM]: Device Addr 0x00 0x00 0x00 0x00 0x00 0x00.
[DM]:[DI 0x03]: Device type 0xFF.
[DM]: Device Addr 0x00 0x00 0x00 0x00 0x00 0x00.
[DM]:[DI 0x04]: Device type 0xFF.
[DM]: Device Addr 0x00 0x00 0x00 0x00 0x00 0x00.
[DM]:[DI 0x05]: Device type 0xFF.
[DM]: Device Addr 0x00 0x00 0x00 0x00 0x00 0x00.
[DM]:[DI 0x06]: Device type 0xFF.
[DM]: Device Addr 0x00 0x00 0x00 0x00 0x00 0x00.
[DM]: Notifying application of event 0x11
[APPL]: device_manager_event_handler
[APPL]: >> DM_EVT_CONNECTION (conn_handle 0)
[APPL]:[CA A4 F4 EA DE 1B]: Connection Established
Starting discovery
[DM]: >> dm_whitelist_create
[DM]: Created whitelist, number of IRK = 0x00, number of addr = 0x00
[DM]: << dm_whitelist_create
[APPL]: << DM_EVT_CONNECTION
[APPL]: on_ble_central_gap_evt BLE_GAP_EVT_CONNECTED
db_discover_evt_handler 0
[GATTC]: gatt block service discovered at peer
Discovery complete
[DM]: >> dm_security_setup_req
[DM]: << dm_security_setup_req, 0x00000000
[DM]: >> BLE_GAP_EVT_SEC_PARAMS_REQUEST
[DM]:[DI 0x00]: Device type 0xFF.
[DM]: Device Addr 0x00 0x00 0x00 0x00 0x00 0x00.
[DM]: Allocated device instance 0x00
[DM]:[CI 0x00]:[DI 0x00]: Bonded!
[DM]: 0x01, 0x01, 0x00, 0x01
[DM]: Security parameter reply request failed, reason 0x00000007.
[APPL]: on_ble_central_gap_evt BLE_GAP_EVT_SEC_PARAMS_REQUEST


device side:
[APPL]: device_manager_event_handler
[APPL]: >> DM_EVT_CONNECTION (conn_handle 3)
[APPL]:[FD 82 F6 90 01 74]: Connection Established
[DM]: >> dm_whitelist_create
[DM]: Created whitelist, number of IRK = 0x00, number of addr = 0x00
[DM]: << dm_whitelist_create
[APPL]: << DM_EVT_CONNECTION
[APPL]: on_ble_peripheral_gap_evt BLE_GAP_EVT_CONNECTED (conn_handle 3)
[DM]: >> BLE_GAP_EVT_SEC_PARAMS_REQUEST
[DM]:[DI 0x00]: Device type 0xFF.
[DM]: Device Addr 0x00 0x00 0x00 0x00 0x00 0x00.
[DM]: Allocated device instance 0x00
[DM]:[CI 0x00]:[DI 0x00]: Bonded!
[DM]: 0x01, 0x01, 0x00, 0x01
[DM]: Notifying application of event 0x13
[APPL]: device_manager_event_handler
[APPL]:[0x00] >> DM_EVT_SECURITY_SETUP
[DM]: >> dm_security_setup_req
[DM]: << dm_security_setup_req, 0x00000008
[APPL]:[0x00] << DM_EVT_SECURITY_SETUP
[APPL]: on_ble_peripheral_gap_evt BLE_GAP_EVT_SEC_PARAMS_REQUEST
[APPL]: on_ble_peripheral_gap_evt BLE_GAP_EVT_AUTH_KEY_REQUEST