Transmission with Record Timing

Transmission with record timing means the records are scheduled on the time tag set for each record.

Each time tag specifies a clock value defining when the record must be transmitted.

The option MXF_TXAPERIODIC_FLAG_USE_RECORD_ABSOLUTE_TIME must be used for this type of transmission.

In the example below, the records are sent based on the absolute clock timing specified in the time tag field for each record.

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;

   //  In the example below the timetag in the record is set
   //  and the option MXF_TXAPERIODIC_FLAG_USE_RECORD_ABSOLUTE_TIME
   //  In this case the records are sent based on the absolute clock
   //  timing specified in the timetag field for each records.

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

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

   currentTime+=100000000;

   // Set the record
      // The scheduling timetag is as follow:
      // clock current time + 100 ms
      // Each record are sent with a timetag of 5 ms interval.

   if(!rc)
   {
      //Prepares records to send for basic transmission/reception test
      for(data=0; data<MAX_TX_RECORDS_TO_TRANSMIT; data++)
      {
         rec->timeTag      = currentTime+(data*5000000);
         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_USE_RECORD_ABSOLUTE_TIME, 0, MAX_TX_RECORDS_TO_TRANSMIT, txHostBuffer);
   }

  ...