MQX event handling vs ISR

[rvigneault]

Hi,

We are using events (not lwevents) to share that ISR has been called.

We are currently opening the event (_event_open) in the ISR but we cannot close the event since _event_close cannot be used in ISRs as documented into the reference manual.

This seems to lead to _event_open failing with MQX_OUT_OF_MEMORY (this happens, we assume that the missing _event_close lead to that error).

How can we either close the event, handle it or event share information safely to a task?

Is it thread-safe to open a lwevent globally and use the instance in the interruption and in a task?

Thanks!

[danielchen]

Hi :

Please refer to the event demo under MQX installation folder. The code shows how a task waits for an event. This event can be set by any other process or interrupt in the system.  The example simulates an ISR event using another simple task.

Freescale_MQX_4_2\mqx\examples\event

Regards

Daniel

[rvigneault]

Hi Daniel,

The example only opens the event (not a lwevent) in the interrupt but never closes it (it cannot since _event_close cannot be called into an interrupt).

void simulated_ISR_task
   (
      uint32_t initial_data
   )
{
   void *event_ptr;

   /* open event connection */
   if (_event_open("event.global",&event_ptr) != MQX_OK) {
      printf("\nOpen Event failed");
      _task_block();
   }

   while (TRUE) {
      _time_delay_ticks(200);
      if (_event_set(event_ptr,0x01) != MQX_OK) {
         printf("\nSet Event failed");
         _task_block();
      }
   }
}

We were also doing that but _event_open ends up returning MQX_OUT_OF_MEMORY after many interrupt calls, which we assume is because too many events are already open for the event name.

It probably works in the example because simulated_ISR_task is not called many times, as would be a normal ISR (in the example it is simulated by created a task calling the function.

Should I assume that full blown events (i.e. not lwevents) cannot be used in ISRs?

Thanks!