BLE adding characteristic doesn´t work

[simon1516]

Hi,

I´m trying to add a new, custom TX characteristic to Softdevice. I use example from SDK 16 "UART/Serial Port Emulation over BLE".

How I can do this, is explained here: "https://infocenter.nordicsemi.com/index.jsp?topic=%2Fsdk_nrf5_v16.0.0%2Fble_sdk_app_nus_eval.html&cp=7_1_4_2_2_25_0_0&anchor=adding_prop_ser_and_char"

So I add the following code to "ble_nus.c":

#define test                           0x0005               /**< The UUID of the test Characteristic. */
memset(&add_char_params, 0, sizeof(add_char_params));
add_char_params.uuid = test;
add_char_params.uuid_type = p_nus->uuid_type;
add_char_params.max_len = BLE_NUS_MAX_TX_CHAR_LEN;
add_char_params.init_len = sizeof(uint8_t);
add_char_params.is_var_len = true;
add_char_params.char_props.notify = 1;

add_char_params.read_access = SEC_OPEN;
add_char_params.write_access = SEC_OPEN;
add_char_params.cccd_write_access = SEC_OPEN;

return characteristic_add(p_nus->service_handle, &add_char_params, &p_nus->tx_handles);

But there is no new TX characteristic in nRF connect App. The both other standard characteristics are addet in similar way.

What I´m doing wrong?

[Edvin]

Hello,

If you checked the return value for characteristic_add using an APP_ERROR_CHECK(err_code) on the return value from the function that this snippet is from, then I suspect that the reason for why your phone doesn't see the new service is that it has cached the services from a previous connection. I just wrote an answer to a similar ticket. Please check it out:

https://devzone.nordicsemi.com/f/nordic-q-a/61171/incorrect-services-on-services-tab-of-nrf-connect-mobile

If that doesn't help, feel free to let me know here.

Best regards,

Edvin

[Edvin]

By the way. In your snippet, you define test as 0x0005. But you don't use "test" anywhere else. Are you sure you are not initializing the same characteristic UUID twice? The BLE_UUID_NUS_TX_CHARACTERISTIC?

[simon1516]

Oh, this was my fault. I corrrected it in my first post. The variable "test" (0x0005) is used for "add_char_params.uuid". But it doesn´t work though.

I turned Bluetooth on and off. It doesn´t help. I changed UUID value for the standard characteristics and build the project again. nRF Connect shows the new UUID´s, so I think thewre is no problem with chache.

Can I do something other?

[simon1516]

I don´t know why, but if I comment out 

return characteristic_add(p_nus->service_handle, &add_char_params, &p_nus->tx_handles);

and add

err_code = characteristic_add(p_nus->service_handle, &add_char_params, &p_nus->tx_handles);
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }

it work´s  :-)

I can now add characteristics as required. Thank you for your help.

I have a second question, maybe you can help me:

The data, which is sent by BLE to nRF connect is handled in the function "uart_event_handle()". Now, I have added four characteristics. The data, recieved from UART, always transmitt to the fourth characteristic.

Where can I see to which characteristic the data is send to? The function "ble_nus_data_send" gives no information about that? Where can I control this?

Thanks in advace!

Simon

[Edvin]

Hello Simon.

So you say that all the data that you send is sent via the last characteristic?

If you look at the implementation of ble_nus_data_send(), you will see that it uses a handle called:

hvx_params.handle = p_nus->tx_handles.value_handle;

So if this handle is used in the implementation of the characteristic, I guess it would always be the last one.

You should add a new handle to all the new characteristics that you add. Look at how the tx_handle is added, compared to the rx_handle in the unmodified example.

Try adding some new handles in:

struct ble_nus_s
{
    uint8_t                         uuid_type;          /**< UUID type for Nordic UART Service Base UUID. */
    uint16_t                        service_handle;     /**< Handle of Nordic UART Service (as provided by the SoftDevice). */
    ble_gatts_char_handles_t        tx_handles;         /**< Handles related to the TX characteristic (as provided by the SoftDevice). */
    ble_gatts_char_handles_t        rx_handles;         /**< Handles related to the RX characteristic (as provided by the SoftDevice). */
    blcm_link_ctx_storage_t * const p_link_ctx_storage; /**< Pointer to link context storage with handles of all current connections and its context. */
    ble_nus_data_handler_t          data_handler;       /**< Event handler to be called for handling received data. */
};

in ble_nus.h, and use these handles instead of the tx_handle when you add the new characteristics.

Then you need to add something in ble_nus_data_send() that can take one extra parameter, which says what characteristic handle that you want to use to send the data.