Discovery of 128bit UUID services confusing

[Tielman]

Hi

I am using sd_ble_gattc_primary_services_discover(conn_handle,0x0001,NULL) to discover primary services on a GATT server. After the first call to this function, I get 2 BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP, BLE_GATTC_EVT_CHAR_DISC_RSP and BLE_GATTC_EVT_DESC_DISC_RSP events:

1. BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP with service count = 2, with 2 Standard BLE services listed and all handles linked
2. BLE_GATTC_EVT_CHAR_DISC_RSP and BLE_GATTC_EVT_DESC_DISC_RSP events
3. BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP with service count = 0 (I guess this means discovery is complete)

I know there are more 128 bit services, but why am I receiving the 2nd event with service count = 0. This tells my code that there are no more services, right? If I do another call to sd_ble_gattc_primary_services_discover(conn_handle,0x000c,NULL), but with the start handle set to the handle of the first 128 bit uuid in the list, it correctly returns with the BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP response and some service info, but just the single event with its corresponding CHAR and DESC events...no second event with "service count = 0". So the first time I call it the response is different to the second time I call it.

So, why am I receiving the second event on the first api call, but not on any other there after?

I'm using the following

• IC: nRF52840
• Softdevice: S140 SDK: nRF5_SDK_13.0.0_04a0bfd
• Example as base: ble_app_hrs_c
• IDE: Eclipse + GCC

Thanks

[Tielman]

This is the response when doing another service request immediately after receiving the first response:

• TESTER:DEBUG:SVC DISCOVERY TO CONN 0x0 from handle 0x1
• TESTER:DEBUG:SVC DISCOVERY START SUCCESS.
• TESTER:INFO:BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP: Count 0x2
• TESTER:INFO:=>Svc SVC Handles: 0x1-0x4 - type:1 - uuid:0x1801
• TESTER:INFO:=>Svc SVC Handles: 0x5-0xb - type:1 - uuid:0x1800
• TESTER:DEBUG:SVC DISCOVERY TO CONN 0x0 from handle 0xc
• TESTER:DEBUG:RESPONSE: Busy.
• TESTER:INFO:BLE_GATTC_EVT_CHAR_DISC_RSP disc 1: 0x2a05 - handle 0x3
• TESTER:INFO:BLE_GATTC_EVT_CHAR_DISC_RSP disc 0: 0x2a05 - handle 0x3
• TESTER:INFO:BLE_GATTC_EVT_DESC_DISC_RSP disc 1: 0x2902 - handle 0x4
• TESTER:INFO:BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP: Count 0x0

[Tielman]

...but when I do the request after the LAST BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP, then it is SUCCESS and I get the next SET of events

[endnode]

It looks like there is immediately after finding 2 primary services attempt to search for characteristics. Are you sure there is no other sd_gattc_xxx function call in your code or in some module you use? Eg. ble_db_discovery ?

[Tielman]

Jan, that's it! Even though I removed all references to db_discovery_start, the callback handler was still receiving the events from the stack via ble_db_discovery_on_ble_evt. I guess this triggered the CHAR and DESC reads automatically in the background!

Thanks so much!