Acquisition with Trigger

A basic acquisition program allows capturing all data received on a bus. In some cases, it is necessary to start capturing the traffic only when a specific event is detected. In this case, the acquisition triggering service can be used for this. Two types of event are supported: trigger on a specific ARINC 708 data word content and trigger on the running state of another channel.

When an acquisition with trigger is started, the received data is not available to the application until the trigger condition(s) are met. In this state, the data received is kept in a circular queue. The maximum number of data records to be kept in the queue is configurable. If the queue is full, the older data are flushed to make place for newly incoming data. When the trigger conditions are realized, the acquisition goes into running state. In this state, the pre-trig data and all newly incoming data are queued until the application reads them (through the mxfA708RxAcqRead() function).
The conditions of the condition list can either be "ANDed" or "ORed" together.

Example

ar708_trigger.c

HMXF_SERVER  server;
HMXF_BUFFER  rxBuffer;
MXF_RXACQ_TRIG_COND_RDATA_DW_PARM condParam;
HMXF_COND_LIST condList=0;
uint64 rxAcqStatus, trigTime=0;
time_t timeTemp;
struct tm * ptm;
char szTime[1024];
uint64 msec, usec;

   ...

   // Sets timebase to computer 64-bit microseconds
   if(!rc)
      rc = mxfSystemTimeBaseSet(server, MXF_TIMEBASE_COMPUTER_USEC);

   // Configures trigger
   // Creates the condition list
   if (!rc)
      rc = mxfRxAcqTrigConditionListAlloc(server, &condList);

   // The condition will be triggered on the 5th record
   if(!rc)
   {
      condParam.mask = 0x01FE0000;
      condParam.data = 0x00000000;
      condParam.offset = 0;
      condParam.options = MXF_RXACQ_TRIG_COND_RDATA_OPTIONS_NOTEQUAL;

      rc = mxfRxAcqTrigConditionAdd(condList, MXF_RXACQ_TRIG_COND_ID_RDATA_DW , &condParam);
   }

   // Set the trigger with a pretrig count of 3 which allows some records to be read before the condition was triggered.
   if(!rc)
      rc = mxfRxAcqTrigSet(rxBuffer, condList, 3);

   if (!rc)
      rc = mxfRxAcqModeSet(rxBuffer, MXF_RXACQ_MODE_CIRCULAR);

   // Starts acquisition
   if(!rc)
      rc = mxfRxAcqStart(rxBuffer, MXF_RXACQ_FLAG_DEFAULT, 0, 0);

   ...

   // Check trigger happened
   if(!rc)
      rc = mxfRxAcqBufferStatusGet(rxBuffer, &rxAcqStatus, NULL, NULL, NULL);
   if(!rc)
   {
      if(rxAcqStatus & MXF_RXACQ_STATUS_TRIG_OCCURRED)
      {
         // Displays the acquisition trigger time
         rc = mxfRxAcqTrigTimeGet(rxBuffer, &trigTime);
         if(!rc)
         {
            timeTemp = trigTime/1000000;
            ptm = localtime(&timeTemp);
            strftime(szTime, sizeof(szTime), "%Y-%m-%d %H:%M:%S", ptm);
            usec = trigTime%1000;
            timeTemp = trigTime/1000;
            msec = timeTemp%1000;
            printf("Event triggered at %s:%03llu:%03llu\n", szTime, msec, usec);
         }
      }
      else
         printf("Trigger not fired\n");
   }

   ...