How to get Central name and unique UUID?

[Clonimmus74]

Hi all,

I use nRF52832 with the UART peripheral example.

I need to get the name and unique UUID of the Central I'm connecting to (after connection).

The Central can either be Android, iOS or nRF52832 with the Central code of the UART example.

I use SDK V15.0.0 and Softdevice V 6.0.0

How do I go about doing that?

I'm am new to BLE and my knowledge is limited, specific detailed answers will be greatly appreciated.

Thank you

[Mttrinh]

Hi,

The device name of the central is contained in the device name characteristic, if it has a name. It can then be extracted through the GATT layer by discovering the service. After you have done a service discovery, you will be able to get the device name and UUID.

Also, if you are using the UART central example, you would need to add a service with a name characteristic.

[Clonimmus74]

I understand I need to use:

sd_ble_gattc_char_value_by_uuid_read

So I did:

             ble_uuid_t p_uuid = {.uuid = BLE_UUID_GAP_CHARACTERISTIC_DEVICE_NAME,.type = BLE_UUID_TYPE_BLE};

             sd_ble_gattc_char_value_by_uuid_read(m_conn_handle, &p_uuid,
            ble_gattc_handle_range_t const *  p_handle_range
            )

As you can see, I have no idea what to put in p_handle_range.

Also, where do I see the response?

[Clonimmus74]

I tried:

  ble_uuid_t p_uuid = {.uuid = BLE_UUID_GAP_CHARACTERISTIC_DEVICE_NAME,.type = BLE_UUID_TYPE_BLE};
  ble_gattc_handle_range_t p_handle_range = {.start_handle = 0x0001, .end_handle = 0xFFFF};

  err_code = sd_ble_gattc_char_value_by_uuid_read(m_conn_handle, &p_uuid, &p_handle_range);
  APP_ERROR_CHECK(err_code);

And received err_code = 17

[Mttrinh]

Hi,

Error code 17 means NRF_ERROR_BUSY, have you checked if anything else is running when you call this function?

Regarding the repsonse, have a look at this message sequence chart. After calling sd_ble_gattc_char_value_by_uuid_read(and it returns success) you will receive an event BLE_GATTC_EVT_CHAR_VAL_BY_UUID_READ_RSP. You will need to handle this in the ble_evt_handler and then you can get the value from p_ble_evt->gattc_evt.params.char_val_by_uuid_read_rsp.handle_value[0].

[Clonimmus74]

What do you mean by "anything else is running"? I execute the code in the BLE_GAP_EVT_CONNECTED event in ble_evt_handler after the execution of nrf_ble_qwr_conn_handle_assign.

I tried also executing the code in main, right after BLE_GAP_EVT_CONNECTED event, before any data exchange is happening.

Do I look for BLE_GATTC_EVT_CHAR_VAL_BY_UUID_READ_RSP event in ble_evt_handler() function?

Thanks.

[Mttrinh]

Hi,

NRF_ERROR_BUSY means that a client procedure is already in progress and you need to try again. You might need to call the function again to test if it’s ready. Adding a timer could be the solution.

You need to add the BLE_GATTC_EVT_CHAR_VAL_BY_UUID_READ_RSP event in the ble_evt_handler.

[Clonimmus74]

Hi,

I tried (in BLE_GAP_EVT_CONNECTED):

do
{
err_code = sd_ble_gattc_char_value_by_uuid_read(m_conn_handle, p_uuid, p_handle_range);
}
while (NRF_ERROR_BUSY == err_code);

and I never get out of the do-while loop....