Cannot send string data over BLE to iOS Nordic Connect app from board.

[rezKamal]

Hi everyone, so I have been trying to enable the nRF52840 to send notifications to the Nordic Connect app via a custom characteristic. The app can detect the custom service when it's being advertised and it connects successfully, but even after I enable Notifications, I cannot receive anything.

I used the ble_app_uart project and changed the main() function so that instead of being in an idle state, it repeatedly tries to send data in an infinite loop:

    BTLE_data[0] = '0';
    BTLE_data[1] = '1';
    BTLE_data[2] = '2';
for (;;) {

      ret_code_t err_code;
    
      uint8_t string[] = "serial updated\n\r";
      uint16_t length = sizeof(string);
    
      do
      {
        
          err_code = ble_nus_string_send(&m_nus, string, &length);
          if ( (err_code != NRF_ERROR_INVALID_STATE) && (err_code != NRF_ERROR_BUSY) )
          {
              APP_ERROR_CHECK(err_code);
          }
      } while (err_code == NRF_ERROR_BUSY);
    }

The other change I made is adding the custom characteristic.

/**@brief Function for adding the Custom Value characteristic.
 *
 * @param[in]   p_nus        Custom Service structure.
 * @param[in]   p_nus_init   Information needed to initialize the service.
 *
 * @return      NRF_SUCCESS on success, otherwise an error code.
 */
static uint32_t custom_char_add(ble_nus_t * p_nus, const ble_nus_init_t * p_nus_init)
{
    uint32_t            err_code;
    ble_gatts_char_md_t char_md;
    ble_gatts_attr_md_t cccd_md;
    ble_gatts_attr_t    attr_char_value;
    ble_uuid_t          ble_uuid;
    ble_gatts_attr_md_t attr_md;

    ble_uuid128_t custom_char_uuid = {CUSTOM_CHAR_UUID_BASE};

    memset(&char_md, 0, sizeof(char_md));

    char_md.char_props.read   = 0;
    char_md.char_props.write_wo_resp  = 1;
    char_md.char_props.notify = 1; 
    char_md.p_char_user_desc  = NULL;
    char_md.p_char_pf         = NULL;
    char_md.p_user_desc_md    = NULL;
    char_md.p_cccd_md         = NULL; 
    char_md.p_sccd_md         = NULL;

    memset(&attr_md, 0, sizeof(attr_md));

    attr_md.read_perm  = p_nus_init->custom_value_char_attr_md.read_perm;
    attr_md.write_perm = p_nus_init->custom_value_char_attr_md.write_perm;
    attr_md.vloc       = BLE_GATTS_VLOC_STACK;
    attr_md.rd_auth    = 0;
    attr_md.wr_auth    = 0;
    attr_md.vlen       = 0;

    ble_uuid.type = p_nus->uuid_type;
    ble_uuid.uuid = CUSTOM_CHAR_UUID;

    err_code = sd_ble_uuid_vs_add(&custom_char_uuid, &p_nus->uuid_type);	// Add new base UUID for add characteristic UUID
    VERIFY_SUCCESS(err_code);

    memset(&attr_char_value, 0, sizeof(attr_char_value));

    attr_char_value.p_uuid    = &ble_uuid;
    attr_char_value.p_attr_md = &attr_md;
    attr_char_value.init_len  = sizeof(uint8_t);
    attr_char_value.init_offs = 0;
    attr_char_value.max_len   = sizeof(uint8_t);

    err_code = sd_ble_gatts_characteristic_add(p_nus->service_handle, &char_md,
                                               &attr_char_value,
                                               &p_nus->custom_value_handles);
                                               
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }

    return NRF_SUCCESS;
}

I tried to figure out what's going on by setting breakpoints, and it seems like it gets stuck in the execution of ble_nus_string_send() because p_nus->conn_handle = BLE_CONN_HANDLE_INVALID.

Any suggestions?

[Vidar Berg]

Hello,

Assume you're using an older SDK version as your ble_nus_data_send() function is not taking the connection handle as an input argument like we do in our more recent SDKs. Please place a breakpoint on the following line in your nus service implementation and see if the connection handle gets assigned on the connection event or not.

[rezKamal]

I am actually using ble_nus_string_send instead of ble_nus_data_send.

I did check the breakpoint though, and it seems that the line of code you highlighted does not get executed, so the conn_handle is never set. How could I fix this?

[Vidar Berg]

Yes, make sure the 'TIMER1_ENABLED' setting is enabled in the sdk_config file. You can also build the project I sent you if you move it to <your sdk folder>\examples\ble_peripheral\ first

[rezKamal]

Thanks. The project does run now, but as soon as I toggle notifications on, I get a fatal error with the local variable info = 0x2b185.

[Vidar Berg]

Please try with the project I sent if you haven't done it already. I made some changes to the logger initialization, so you should see the debug log messages in the Segger debug terminal when you debug the application. The info variable does not tell us where the error occured.

[rezKamal]

Hi, I did try with the project you sent, and it gives a more descriptive error message:

<error> app: ERROR 19 [NRF_ERROR_RESOURCES] at ble_app_uart\main.c:1045
PC at: 0x00030B2F
<error> app: End of error report

[Vidar Berg]

Ok, but you are not using the main.c file I sent. You should replace NRF_ERROR_BUSY with NRF_ERROR_RESOURCES like I did.