Basic Transmission

The basic transmission method consists of sending one or more data records on the data bus and does not care about any timing considerations between the records.

This is the most basic method of sending data. The example below shows all the steps required to build a basic ARINC 429 transmission function.

• How to initialize and set a transmit channel was discussed in a previous section.
• Allocate the specific aperiodic buffer for transmission
• Build the data record.
  • The time tag is set to 0 ; transmit as soon as possible.
  • The repeat count is set to 1 ; the record will not be repeated.
  • The function mxfA429ArwCompose() is used to build the word.
• Finally, mxfA429TxAperiodicWrite() with MXF_TXAPERIODIC_FLAG_DEFAULT flag must be used.

Example

ar429_aperiodic.c

#define BUFFER_SIZE     4096 // 4KB
#define MAX_TX_RECORDS_TO_TRANSMIT 8

HMXF_SERVER server;
HMXF_CHANNEL txChannel;
HMXF_BUFFER  txBuffer=0;
MXF_A429_DATAREC *rec429=NULL;
MXF_A429_DATAREC *rec;
uint32 label, sdi, data, ssm, parity;
uint32 record;
uint64 delay100ms = 100000;
uint32 rc;

   ...

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

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

   // Allocates host buffer
   if (!rc)
   {
      rec429 = (MXF_A429_DATAREC*)malloc(BUFFER_SIZE);
      if (!rec429)
         rc = MAXT_ERROR_MEM;
   }

   // Sets the records: ARINC 429 LABEL=005, SDI=1
   rec = rec429;
   for (record=0; record < MAX_TX_RECORDS_TO_TRANSMIT && !rc; record++)
   {
      rec->timeTag = 0;
      rec->control = 0;
      rec->repeatCount = 1;
      rec->reserved = 0;

      label = 5;
      sdi = 1;
      data = record*8;
      ssm = 0;
      parity = VMXF_A429_PARITY_ODD;
      rc = mxfA429ArwCompose(label, sdi, data, ssm, parity, &rec->data);
      if(!rc)
         rc = mxfA429NextDataRecordPtrGet(rec, &rec);
    }

    // Transmits the array of records
    if (!rc)
        rc = mxfA429TxAperiodicWrite(txBuffer, MXF_TXAPERIODIC_FLAG_DEFAULT, delay100ms, MAX_TX_RECORDS_TO_TRANSMIT, rec429);

    if (rec429)
      free(rec429);

   ...