Discovering BLE server and characteristic is Nordic Central mode

[chandan]

Hello, I have custom BLE service and characteristic as below image.

I wanted to discover them in ble central mode. I have modified ble_hrc_c.c to validate but central not able to discover. Can anyone suggest? Also attaching code.

[Sigurd]

Hi,

have custom BLE service and characteristic

I wanted to discover them in ble central mode. I have modified ble_hrc_c.c to validate but central not able to discover.

 Since you are using a custom service/characteristic, I recommend taking a look at the central examples that also uses custom/vendor specific service/characteristic, e.g. the ble_app_uart_c and ble_app_blinky_c

[chandan]

Yes, I checked, But I am unable to make it work. I pasted my code too. I am not able to find mistakes in my code. 

[Sigurd]

E.g. the type you passed to ble_db_discovery_evt_register() is wrong, it should be BLE_UUID_TYPE_VENDOR_BEGIN. Again, since you are using a custom service/characteristic, I recommend taking a look at the central examples that also uses custom/vendor specific service/characteristic, e.g. the ble_app_uart_c and ble_app_blinky_c. 

[chandan]

I have updated but still not working. Looking into the ble_app_uart_c and ble_app_blinky_c  tooo

[Sigurd]

Did you implement the BLE Peripheral as well?

Do you have a requirement for different base UUIDs in your project?

What is usually recommended is to use a 128-bit vendor specific UUID which will look something like this "4A98xxxx-1CC4-E7C1-C757-F1267DD021E8" as a “base UUID”. The four x’s represent a field where you will insert your own 16-bit IDs for your custom services and characteristics and use them just like a predefined UUID. You will have different customs UUID for each service and characteristic but only one "base UUID".

[chandan]

I know that but  BLE Peripheral is already implemented and in production. So we can't change it

[chandan]

it wouldn't discover with the below code

uint32_t ble_lbs_c_init(ble_lbs_c_t * p_ble_lbs_c, ble_lbs_c_init_t * p_ble_lbs_c_init)
{
    uint32_t      err_code;
    ble_uuid_t    lbs_uuid;
    ble_uuid128_t   service_base_uuid =  {0x4b, 0x91, 0x31, 0xc3, 0xc9, 0xc5, 0xcc, 0x8f,
                              0x9e, 0x45, 0xb5, 0x1f, 0x00, 0x00, 0xaf, 0x4f};
                            

    ble_uuid128_t   characteristic_base_uuid =  {0xa8, 0x26, 0x1b, 0x36, 0x07, 0xea, 0xf5, 0xb7,
                              0x88, 0x46, 0xe1, 0x36, 0x00, 0x00, 0xb5, 0xbe};


    VERIFY_PARAM_NOT_NULL(p_ble_lbs_c);
    VERIFY_PARAM_NOT_NULL(p_ble_lbs_c_init);
    VERIFY_PARAM_NOT_NULL(p_ble_lbs_c_init->evt_handler);


    p_ble_lbs_c->uuid_type = BLE_UUID_TYPE_VENDOR_BEGIN;

    //err_code = sd_ble_uuid_vs_add(&lbs_base_uuid, &p_ble_lbs_c->uuid_type);
    err_code = sd_ble_uuid_vs_add(&service_base_uuid, &p_ble_lbs_c->uuid_type);
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }
    VERIFY_SUCCESS(err_code);

    err_code = sd_ble_uuid_vs_add(&characteristic_base_uuid, &p_ble_lbs_c->uuid_type);
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }
    VERIFY_SUCCESS(err_code);

    lbs_uuid.type =  p_ble_lbs_c->uuid_type;
    lbs_uuid.uuid = LBS_UUID_SERVICE;

    p_ble_lbs_c->peer_lbs_db.button_cccd_handle = BLE_GATT_HANDLE_INVALID;
    p_ble_lbs_c->peer_lbs_db.button_handle      = BLE_GATT_HANDLE_INVALID;
    p_ble_lbs_c->peer_lbs_db.led_handle         = BLE_GATT_HANDLE_INVALID;
    p_ble_lbs_c->conn_handle                    = BLE_CONN_HANDLE_INVALID;
    p_ble_lbs_c->evt_handler                    = p_ble_lbs_c_init->evt_handler;


    return ble_db_discovery_evt_register(&lbs_uuid);
}

but when I change lbs_uuid.type to 0, I am getting NRF_ERROR_INVALID_PARAM at ble_db_discovery_start().

uint32_t ble_lbs_c_init(ble_lbs_c_t * p_ble_lbs_c, ble_lbs_c_init_t * p_ble_lbs_c_init)
{
    uint32_t      err_code;
    ble_uuid_t    lbs_uuid;
    ble_uuid128_t   service_base_uuid =  {0x4b, 0x91, 0x31, 0xc3, 0xc9, 0xc5, 0xcc, 0x8f,
                              0x9e, 0x45, 0xb5, 0x1f, 0x00, 0x00, 0xaf, 0x4f};
                            

    ble_uuid128_t   characteristic_base_uuid =  {0xa8, 0x26, 0x1b, 0x36, 0x07, 0xea, 0xf5, 0xb7,
                              0x88, 0x46, 0xe1, 0x36, 0x00, 0x00, 0xb5, 0xbe};


    VERIFY_PARAM_NOT_NULL(p_ble_lbs_c);
    VERIFY_PARAM_NOT_NULL(p_ble_lbs_c_init);
    VERIFY_PARAM_NOT_NULL(p_ble_lbs_c_init->evt_handler);


    p_ble_lbs_c->uuid_type = BLE_UUID_TYPE_VENDOR_BEGIN;

    //err_code = sd_ble_uuid_vs_add(&lbs_base_uuid, &p_ble_lbs_c->uuid_type);
    err_code = sd_ble_uuid_vs_add(&service_base_uuid, &p_ble_lbs_c->uuid_type);
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }
    VERIFY_SUCCESS(err_code);

    err_code = sd_ble_uuid_vs_add(&characteristic_base_uuid, &p_ble_lbs_c->uuid_type);
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }
    VERIFY_SUCCESS(err_code);

    lbs_uuid.type =  0 ; //p_ble_lbs_c->uuid_type;
    lbs_uuid.uuid = LBS_UUID_SERVICE;

    p_ble_lbs_c->peer_lbs_db.button_cccd_handle = BLE_GATT_HANDLE_INVALID;
    p_ble_lbs_c->peer_lbs_db.button_handle      = BLE_GATT_HANDLE_INVALID;
    p_ble_lbs_c->peer_lbs_db.led_handle         = BLE_GATT_HANDLE_INVALID;
    p_ble_lbs_c->conn_handle                    = BLE_CONN_HANDLE_INVALID;
    p_ble_lbs_c->evt_handler                    = p_ble_lbs_c_init->evt_handler;


    return ble_db_discovery_evt_register(&lbs_uuid);
}

[chandan]

I have 2 services. One has 3 and another got 1 characteristic. For now I just want to discover only 1 characteristic.

[Sigurd]

Maybe this post can be helpful: https://devzone.nordicsemi.com/f/nordic-q-a/36462/discovering-problem-for-different-128-bit-service-and-characteristic-uuid-as-a-central-device/197482#197482