BLE interrupt priority question and BLE event lost issue

RE: BLE interrupt priority question and BLE event lost issue

Ian — Tue, 14 Nov 2017 02:33:35 GMT

I call SendDatas() in main loop every 10ms:

int main(void)
{
     init code

     for(;;)
     {
          if (timer told me 10ms is passed)
          {
                 SendDatas();
          }

          other code
     }
}

Actually it seems the problem is resolved, I test from yesterday to now the program work well, I take RK's advice and modify my code as this:

The code when receive BLE_EVT_TX_COMPLETE event:

   case BLE_EVT_TX_COMPLETE:
            for (uint8_t i = 0; i < CENTRAL_LINK_COUNT; i++)
            {
                if (p_gap_evt->conn_handle == m_conn_handle_nus_c[i])
                {
                    CRITICAL_REGION_ENTER();
                    m_conn_tx_packet_count[i] += p_ble_evt->evt.common_evt.params.tx_complete.count;
                    CRITICAL_REGION_EXIT();
                    
                    break;
                }
            }
            break;

The SendDatas funciton:

 bool SendDatas(ptSendPar pars)
    {
          //some code
    
         while (there are datas to send)
         {
              while (1)     //while loop until time out or BLE disconnect or data send succuss
              {
                  while (m_conn_tx_packet_count[pars->peripheral_id] == 0)  //wait free tx packet 
                  {
                      if (timeout)
                      {
                          return false;
                      }
         
                     if (disconnect)
                     {
                          return false;
                     }
                  }
    
                 if (ble_nus_c_string_send(p_ble_nus_c, &txbuf[send_index], len) == NRF_SUCCESS)
                 {
                      CRITICAL_REGION_ENTER();
                      m_conn_tx_packet_count[pars->peripheral_id]--;
                      CRITICAL_REGION_EXIT();
                    
                      break;
                  }
    
                  the length of datas to send -= len
           }
    }

The difference between the new code and the old code is:

1、new code use m_conn_tx_packet_count[i] += p_ble_evt->evt.common_evt.params.tx_complete.count; and the old code use just m_conn_tx_packet_count[i] ++;

2、new code use CRITICAL_REGION_ENTER and CRITICAL_REGION_EXIT then write m_conn_tx_packet_count

I still do not understand why the old code will cause this problem(m_conn_tx_packet_count always be 0), even p_ble_evt->evt.common_evt.params.tx_complete.count is greater than 1 and i only increase m_conn_tx_packet_count by 1, it just will let the max value of m_conn_tx_packet_count less than it should be but will not make m_conn_tx_packet_count be 0.

So is CRITICAL_REGION_ENTER and CRITICAL_REGION_EXIT solved my problem? I remember I used them before and there is still this problem, but I'm not so sure and I'm going to do more test about this.

Anyone know what's the exactly issue in my old code? Any suggest will be helpful~

RE: BLE interrupt priority question and BLE event lost issue

Petter Myhre — Mon, 13 Nov 2017 14:57:32 GMT

I don't know exactly when you call SendDatas(), but as RK mentioned, you don't necessarily receive one BLE_EVT_TX_COMPLETE for every time you send a write command, you have a count field that tells you have many was sent. If you get an unexpected m_conn_tx_packet_count of 0 you can try to do some printfs to figure out why it ends up at 0.

RE: BLE interrupt priority question and BLE event lost issue

Ian — Mon, 13 Nov 2017 03:47:00 GMT

I also believe that the Nordic will not make such a mistake. But if so I really can not explain what happened to my program, include the last question "nrf_dfu_wait never return if I do not disable uart".

RE: BLE interrupt priority question and BLE event lost issue

RK — Mon, 13 Nov 2017 03:38:52 GMT

BLE events never get lost. The stack has the highest priority of all, all events it generates it queues up until you find time to receive them. It never loses TX events or callbacks telling you a buffer is available. It just doesn't.

RE: BLE interrupt priority question and BLE event lost issue

Ian — Mon, 13 Nov 2017 03:33:19 GMT

If other ISR with priority equal to or higher than the priority of SD_EVT_IRQn cost too much time(e.g. APP TIMER event handler), the ble_event_handler cannot be executed in time，the BLE events also don't get lost in this case?

RE: BLE interrupt priority question and BLE event lost issue

RK — Mon, 13 Nov 2017 03:27:58 GMT

BLE events don't get lost, ever.

RE: BLE interrupt priority question and BLE event lost issue

Ian — Mon, 13 Nov 2017 03:25:44 GMT

I debug the program again, I watch NVIC_IP register and call NVIC_GetPriority(SD_EVT_IRQn) function,they all showed that the priority of SD_EVT_IRQn is 3! In this case,maybe my other interrupt which the priority is also 3 cause the SD EVENT lost i guess. But 3 is the lowest priority i can use, I have no choice without it, unless I do not use interrupt.

I tried change the priority of SD_EVT_IRQn use NVIC_SetPriority(SD_EVT_IRQn, 2), but no matter where i use it (e.g. before or after SOFTDEVICE_HANDLER_INIT,before or after softdevice_enable_get_default_config, before or after softdevice_enable) the program will crash.

In conclusion, there are two questions I want to confirm:

1、Will my interrupt with the same priority of SD_EVT_IRQn cause BLE EVENT lost?

2、How can I set or change the priority of SD_EVT_IRQn?

RE: BLE interrupt priority question and BLE event lost issue

Ian — Mon, 13 Nov 2017 03:07:39 GMT

Oh that's my carelessness, but this will not cause my problem, if every time ble_nus_c_string_send return NRF_SUCCESS I can receive BLE_EVT_TX_COMPLETE event, m_conn_tx_packet_count will never be 0 after the old ble_nus_c_string_send success and the new ble_nus_c_string_send be called.But my problem is sometimes m_conn_tx_packet_count always be 0.

RE: BLE interrupt priority question and BLE event lost issue

RK — Sun, 12 Nov 2017 21:25:49 GMT

I haven't read all the way through your entire application however

Documentation for ble_evt_tx_complete_t

Data Fields
uint8_t 	count

but you are always assuming the count is one and using '++'