BLE_NUS_EVT_COMM_STARTED not sent

[NickH]

Hi,

I have been using the NUS service via the ble_app_uart example on SDK 16 in conjunction with the nRF Connect iOS app and all works fine.

I connect via the iOS app and when I select the notify button on the iOS app corresponding to the UART TX Characteristic, I get the BLE_NUS_EVT_COMM_STARTED notification.

At this point, I can send and receive data and when I send data,  I get the BLE_NUS_EVT_TX_RDY notification to indicate the send completed.

However, when I port the example code into my own nRF52 app,  I do not get the BLE_NUS_EVT_COMM_STARTED notification.  I can receive data from the iOS app but when I try to send I get NRF_ERROR_INVALID_STATE from sd_ble_gatts_hvx() in ble_nus_data_send() which I guess is consistent with the NUS service not being ready.

The code appears identical but clearly I missing something - if anyone can suggest what I might have missed for the BLE_NUS_EVT_COMM_STARTED not to be sent, I would be very grateful...

static void nus_data_handler(ble_nus_evt_t * p_evt)
{

   char rxData[20] = {0};

   bleNUS_TX_RDY = false;

   //NRF_LOG_INFO("Received event from NUS %d\n",p_evt->type);

   switch(p_evt->type)
   {
      case BLE_NUS_EVT_COMM_STARTED:
          NRF_LOG_INFO("BLE_NUS_EVT_COMM_STARTED.\n");
          break;
      case BLE_NUS_EVT_COMM_STOPPED:
          NRF_LOG_INFO("BLE_NUS_EVT_COMM_STOPPED.\n");
          break;
      case BLE_NUS_EVT_TX_RDY:
          NRF_LOG_INFO("BLE_NUS_EVT_TX_RDY.\n");
          bleNUS_TX_RDY = true;
          break;
      case BLE_NUS_EVT_RX_DATA:
          NRF_LOG_INFO("BLE_NUS_EVT_RX_DATA.\n");
          NRF_LOG_HEXDUMP_DEBUG(p_evt->params.rx_data.p_data, p_evt->params.rx_data.length);
          memcpy(rxData,p_evt->params.rx_data.p_data,p_evt->params.rx_data.length);
          NRF_LOG_INFO("rxData >%s<\n",rxData);
          printf("rxData >%s<\n",rxData);          
          break;
      default:
          NRF_LOG_INFO("RX default %d\n",p_evt->type);
          break;
    }
}


Log from working example code: 
 app: Debug logging for UART over RTT started.
 app: Connected
 app: Data len is set to 0xB6(182)
 app: ATT MTU exchange completed. central 0xF7 peripheral 0xF7
 app: PHY update request.
 app: ATT MTU exchange completed. central 0xF7 peripheral 0xF7
 app: BLE_NUS_EVT_COMM_STARTED.

Log from same function ported to my app:

 app: Connection 0x1 established
 app: Data len is set to 0xB6(182)
 app: ATT MTU exchange completed. Central 0xF7 Peripheral 0xF7
 app: PHY update request.
 app: ATT MTU exchange completed. Central 0xF7 Peripheral 0xF7

[Edvin]

Well, you can't send notifications because it is not enabled. I assume that you have enabled notifications from the central (phone?) when you use your custom app as well? What is your central? A phone or another nRF?

Can you compare the on_write() function in ble_nus.c and see why the BLE_NUS_EVT_COMM_STARTED is not generated with your custom app, but it is with the ble_app_uart example?

BR,

Edvin

[NickH]

Interestingly, I am getting the events in the on_write() that correspond to BLE_NUS_EVT_COMM_STARTED and BLE_NUS_EVT_COMM_STOPPED but p_client == NULL for these events so the events are not registered correctly.

[NickH]

Ah, the issue is in blcm_link_ctx_get() I am getting a NRF_ERROR_NO_MEM which seems to be related to 

p_link_ctx_storage->max_links_cnt

I guess I need to increase some memory some place...

[Edvin]

Does your on_write() function start like this?

static void on_write(ble_nus_t * p_nus, ble_evt_t const * p_ble_evt)
{
    ret_code_t                    err_code;
    ble_nus_evt_t                 evt;
    ble_nus_client_context_t    * p_client;
    ble_gatts_evt_write_t const * p_evt_write = &p_ble_evt->evt.gatts_evt.params.write;

    err_code = blcm_link_ctx_get(p_nus->p_link_ctx_storage,
                                 p_ble_evt->evt.gatts_evt.conn_handle,
                                 (void *) &p_client);
    if (err_code != NRF_SUCCESS)
    {
        NRF_LOG_ERROR("Link context for 0x%02X connection handle could not be fetched.",
                      p_ble_evt->evt.gatts_evt.conn_handle);
    }

    memset(&evt, 0, sizeof(ble_nus_evt_t));
    evt.p_nus       = p_nus;
    evt.conn_handle = p_ble_evt->evt.gatts_evt.conn_handle;
    evt.p_link_ctx  = p_client;

    if ((p_evt_write->handle == p_nus->tx_handles.cccd_handle) &&
        (p_evt_write->len == 2))
    {
        if (p_client != NULL)
        {

And p_client is not set to something other than NULL after

    err_code = blcm_link_ctx_get(p_nus->p_link_ctx_storage,
                                 p_ble_evt->evt.gatts_evt.conn_handle,
                                 (void *) &p_client);

?

What does blcm_link_ctx_get() return? That is, what is err_code after this call?

Be aware that on_write is called in other events as well. Not necessarily only when enabling notifications, and not necessarily only for events in the ble_nus events, but if you write something to one of the characteristics from your central the on_write event will also be triggered. Make sure that you check the event when you actually enable notifications.

BR,

Edvin

[NickH]

Edvin,

I'm pretty certain the event is the BLE_NUS_EVT_COMM_STARTED as it is triggered via nRF Connect app button and same action when connected to sample code ble_app_uart gives the BLE_NUS_EVT_COMM_STARTED event.

My on_write() looks same as yours and the error code after call to blcm_link_ctx_get() is 4.

I did try increasing NRF_CLI_BLE_UART_MAX_CLIENTS to 8 (other forum post) but this made no difference....

Any suggestions?

Nick

[NickH]

Debug Output on ble_app_uart:

 ble_nus: on_write: event received from BLE stack.

 ble_nus: on_write: BLE_NUS_EVT_COMM_STARTED event received.

 app: BLE_NUS_EVT_COMM_STARTED.

 ble_nus: on_write: event received from BLE stack.

 ble_nus: on_write: BLE_NUS_EVT_COMM_STOPPED event received.

 app: BLE_NUS_EVT_COMM_STOPPED.

Debug on custom app:

 ble_nus: on_write: event from BlE stack

 ble_nus: Link context for 0x01 connection handle could not be fetched.

 ble_nus: Link context error 0x04

 ble_nus: on_write: event from BlE stack

 ble_nus: Link context for 0x01 connection handle could not be fetched.

 ble_nus: Link context error 0x04

[NickH]

I managed to fix the memory issue by changing NRF_SDH_BLE_PERIPHERAL_LINK_COUNT from 3 to 1

Thanks for the pointers.....

[Edvin]

Then I interpret this as you managed to get the notification event?

[NickH]

Edvin,

Yes, event was being received but because of the memory error, it was not being registered as a BLE_NUS_EVT_COMM_STARTED.  Fixing the memory error resolved this.

Thanks for your help!

Nick