Updating Periodic Messages

While a schedule runs, the CAN data can be updated asynchronously by the main application using the mxfCanBusTxPeriodicUpdateMsgWrite() function.

The next example shows how to use some functions for updating a transmission buffer.

Scheduling a Single Message

The program below shows how to define a single record with mxfTxPeriodicScheduleSingleMsgAdd() to schedule what will be later updated while the schedule runs.

The example in the next section shows how to update the records dynamically.

#define BUFFER_SIZE     4096 // 4KB

uint32 rc;
HMXF_SCHED schedule=0;
HMXF_SCHED_MSG msgSched;
HMXF_CHANNEL channel;
HMXF_BUFFER txBuffer=0;
MXF_CANBUS_DATAREC *hostBuffer=NULL;

   ...

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

   // Sets the Periodic Scheduler
   if(!rc)
      rc = mxfTxPeriodicScheduleNew(channel, &schedule);

   // Sets scheduling values: Rate=25 ms, Phase=0 us
   if(!rc)
      rc = mxfTxPeriodicScheduleSingleMsgAdd(schedule, 25000000ll, 0, txBuffer, &msgSched);

   // Runs the schedule
   if(!rc)
      rc = mxfTxPeriodicScheduleRun(schedule);

   // Sends messages for 2 seconds
   if(!rc)
   {
      printf("Running periodic transmission...\n\r");
      mxfSleep(2000);
      rc = mxfTxPeriodicScheduleFree(schedule);
   }

   ...

Updating the buffer

The value of the data sent (CAN data) can be updated while a background schedule runs.

The example below shows how the mxfCanBusTxPeriodicUpdateMsgWrite() function can be used to perform the update operation.

#define TXALMOSTFULL    7

uint32 rc=0;
uint32 i;
MXF_CANBUS_DATAREC *recPtr=hostBuffer;
static uint64 data=0;

   ...

   // Refills the FIFO in order to produce a ramp
   for(i=0; !rc && i<TXALMOSTFULL; i++)
   {
      recPtr->timeTag=0;
      recPtr->control=0;
      recPtr->repeatCount=1;
      recPtr->reserved=0;

      rec->id = 0x080A0000;
      rec->info = MXF_CANBUS_REC_INFO_EXTENDED | 8;
      for (i = 0; i<rec->dataSize; i++)
         rec->data[i] = (uint8)data;

      data++;
      rc = mxfCanBusNextDataRecordPtrGet(recPtr, &recPtr);
   }

   // Adds more data to the buffer
   if(!rc)
      rc = mxfCanBusTxPeriodicUpdateMsgWrite(buffer, i, hostBuffer);

   ...