RTOS/TM4C1290NCPDT: SSI not sending all data inserted into transmit register (6 bytes)

Part Number: TM4C1290NCPDT

Tool/software: TI-RTOS

Hello all,

I am having an issue where about 5% of the time, the SSI transfer I am initiating is not sending the full 6 bytes.  Sometimes it will only send 2,3,4, or 5 bytes.  I am looking at this on a scope to verify this.  I will post my initialization and SSI code below. Now the interesting thing is that my check to ensure that all 6 byes were sent never fails (numFailed is always 0).

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void setup_spi_for_onboard_com(void)
{
  uint32_t lnTemp;
  Hwi_Params SSI3_interruptParams;
  Hwi_Handle SSI3_interrupt;

  IntDisable(SSI_MODULE_INT);
  SSIDisable(SSI_MODULE_BASE);
  SysCtlPeripheralReset(SYSCTL_PERIPH_SSI3);

  /*
   * Register SSI3 interrupt handler.
   * */
  Hwi_Params_init(&SSI3_interruptParams);
  SSI3_interruptParams.enableInt = false;
  SSI3_interruptParams.instance->name = "SSI3_interrupt";
  SSI3_interrupt = Hwi_create(71, SSIIntHandler, &SSI3_interruptParams, NULL);

  //Configure SSI3
  SSIConfigSetExpClk(SSI_MODULE_BASE, 120000000 /* SysCtlClockGet() */, SSI_FRF_MOTO_MODE_1, SSI_MODE_MASTER, 6250000, 8);

  Hwi_enableInterrupt(71);

  // Enable receive and TX End of Transmission interrupts
  SSIIntEnable(SSI_MODULE_BASE, SSI_TXEOT | SSI_RXTO);

  IntEnable(SSI_MODULE_INT);
  SSIEnable(SSI_MODULE_BASE);

}

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int32_t sendPackettoKinetis(PowerTecTx_Packet packet)
{
  int32_t key, val;
  int32_t numWritten = 0;
  uint8_t i = 0;
  key = LE_resource_lockwt(SPI_R, WAIT_FOREVER);

  spiTxKinetisMsgBuffer[0] = (uint8_t)0xAA;//(packet.setPoint >> 8);
  spiTxKinetisMsgBuffer[1] = (uint8_t)0xAA;//(packet.setPoint);
  spiTxKinetisMsgBuffer[2] = (uint8_t)0xAA;//(packet.reserved >> 8);
  spiTxKinetisMsgBuffer[3] = (uint8_t)0xAA;//(packet.reserved);
  spiTxKinetisMsgBuffer[4] = (uint8_t)0xAA;//(packet.command);
  spiTxKinetisMsgBuffer[5] = (uint8_t)0xAA;//packet.crc_checksum;

  for(i=0; i<6; i++){
    val = SSIDataPutNonBlocking(SSI_MODULE_BASE, (uint32_t )spiTxKinetisMsgBuffer[i]);
    if (val>0){
      numWritten += val;
      spiBytesSent++;
    }
  }

  while (SSIBusy(SSI_MODULE_BASE)){
    LE_thread_sleep(100);
  }

  LE_resource_unlock(SPI_R, key);

  if(numWritten !=6 ){
    numFailed++;
    return(0); //Error, should always do 6 bytes
  }
  numSent++;
  return(1);
}