Transmission with Absolute Timing

The option MXF_TXAPERIODIC_FLAG_ABSOLUTE_START_TIME is used for starting a transmission at a specific start time in the future.

In this example, the transmission start time is based on the device clock + 100ms in the future, then the records are sent back-to-back.

ar708_aperiodic.c

uint32 rc;
size_t txBufferSize;
HMXF_CHANNEL txChannel;
HMXF_BUFFER txBuffer;
MXF_A708_DATAREC * txHostBuffer;
MXF_A708_DATAREC* rec;
uint32 delay100ms = 100000000;
uint64 currentTime;
uint64 data, word;

   ...


   // Allocates 4 KB buffer for tx data
   if(!rc)
   {
      txBufferSize = 4*1024;

      // Allocates TX Aperiodic static buffer for HIGH priority queue
      rc = mxfTxAperiodicBufferAlloc(txChannel, MXF_TXAPERIODIC_PRIORITY_HIGH, txBufferSize, &txBuffer, NULL);

      // Host buffer allocation
      if(!rc)
      {
         txHostBuffer = (MXF_A708_DATAREC*)calloc(1, txBufferSize);
         if(!txHostBuffer)
            rc = MAXT_ERROR_MEM;
      }
   }

   ...

   rec=txHostBuffer;

   // Get the current time
   rc = mxfDeviceTimerGet(device, &currentTime);
   if (rc)
      return rc;

   //  In the example below the option MXF_TXAPERIODIC_FLAG_ABSOLUTE_START_TIME
   //  is used. In this case the records are sent freely (no time clock control)
   //  with a start transmission time based on the device clock + 100ms in the future.

   printf("\nAperiodic transmission (Absolute)\n");

   if(!rc)
   {
      //Prepares records to send for basic transmission/reception test
      for(data=0; data<MAX_TX_RECORDS_TO_TRANSMIT; data++)
      {
         rec->timeTag      = 0;
         rec->control      = 0;
         rec->repeatCount  = 1;
         rec->manchesterBitErr = 0;
         rec->dataSize     = 200;  //200 bytes corresponds to 1600 bits (see ARINC 708 specification)
         for(word=0; word < rec->dataSize/2; word++)
         {
            switch(word)
            {
            case 0:
               rec->data[word] = 055; // Label 055
               break;
            case 1:
            case 2:
            case 3:
               rec->data[word] = 0x0000;
               break;
            default:
               rec->data[word] = (uint16)(0x0101*data);
            }
         }
         rc = mxfA708NextDataRecordPtrGet(rec, &rec);
      }
   }

   // Transmit the array of records
   if(!rc)
   {
      printf("Transmitting ...\n");
      rc = mxfA708TxAperiodicWrite(txBuffer, MXF_TXAPERIODIC_FLAG_ABSOLUTE_START_TIME, currentTime+delay100ms, MAX_TX_RECORDS_TO_TRANSMIT, txHostBuffer);
   }

  ...