nrf52 unable to enable notifications on the client side ( CCCD not discovered )

RE: nrf52 unable to enable notifications on the client side ( CCCD not discovered )

JJJSchmidt — Sun, 12 Apr 2020 08:45:35 GMT

This problem is solved in Hung Bui's answer to this question. When not using the peer manager, you must handle the BLE_GATTS_EVT_SYS_ATTR_MISSING event in your BLE event handler function. The blinky example includes this case in the function ble_evt_handler() in main.c:

       case BLE_GATTS_EVT_SYS_ATTR_MISSING:
            // No system attributes have been stored.
            err_code = sd_ble_gatts_sys_attr_set(m_conn_handle, NULL, 0, 0);
            APP_ERROR_CHECK(err_code);
            break;

I burned many hours trying to work this out. Some comments in the code relating this event to the CCCD, or better that this enables the client's discovery of the CCCD, would have been a big help!

RE: nrf52 unable to enable notifications on the client side ( CCCD not discovered )

Kenneth — Mon, 03 Dec 2018 15:28:54 GMT

When calling characterisic_add() you get the handle for the specific characteristic you just initialized, every time the peer write to a characteristic you will be notified with a BLE_GATTS_EVT_WRITE event and the handle it write to. Maybe you can output to UART.

RE: nrf52 unable to enable notifications on the client side ( CCCD not discovered )

David — Mon, 03 Dec 2018 12:02:52 GMT

Can you explain more kenneth, I dont fully understand

RE: nrf52 unable to enable notifications on the client side ( CCCD not discovered )

Kenneth — Mon, 03 Dec 2018 08:30:11 GMT

Check the value handle when initialise the characteristic vs. the BLE_GATTS_EVT_WRITE event when the peer write to the individual value handles to enable the cccd's?

Best regards,
Kenneth

RE: nrf52 unable to enable notifications on the client side ( CCCD not discovered )

David — Sun, 02 Dec 2018 10:03:30 GMT

Yes, I see. Do you have any other insights kenneth? What could cause a problem like this?

RE: nrf52 unable to enable notifications on the client side ( CCCD not discovered )

Kenneth — Thu, 29 Nov 2018 19:03:34 GMT

You can see that blinky example does not use peer manager, yet it is using notifications. From the ble_lbs_init() in ble_lbs.c:

RE: nrf52 unable to enable notifications on the client side ( CCCD not discovered )

David — Thu, 29 Nov 2018 12:38:43 GMT

Yes, Kenneth, I have tried the blinky example, displays the ble device but I don't think it has notifications built in. Could this have something to do with the peer manager that I disabled?

RE: nrf52 unable to enable notifications on the client side ( CCCD not discovered )

Kenneth — Thu, 29 Nov 2018 12:23:30 GMT

Very odd, the permissions seems to be set to BLE_GAP_CONN_SEC_MODE_SET_OPEN(), so no security should be needed.

Have you tried some of the SDK examples, such as:
\nRF5_SDK_15.2.0_9412b96\examples\ble_peripheral\ble_app_blinky

The documentation can be found:
http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.2.0/ble_sdk_app_blinky.html?cp=4_0_0_4_1_2_3

Best regards,
Kenneth