SPI transfer takes too much time - ADuCM350

Hello,

I am trying to create a sine wave generator using a DAC and I communicate wth it over SPI. The problem is that the "adi_SPI_MasterTransfer" function in the ADuCM350 SDK does not allow me to transfer data fast enough.

With the 8MHz clock frequency and only sending 3 bytes per point from a lookup table (256 points max) to the DAC I gant only reach a sine wave of 42Hz.

How could I decrease the time needed to send data ?

Here is my SPI function I use:

void SPI_DAC(uint16_t DACreg)
{
  
  gTransmitBuffer[0] = 0x00;
  gTransmitBuffer[1] = ((uint8_t)((DACreg>>8) & 0xFF));
  gTransmitBuffer[2] = (DACreg & 0xFF);

  gPrologueBuffer[0]             = 0x00;
  transceive.pPrologue            = gPrologueBuffer;
  transceive.PrologueSize         = 0;
  transceive.pTxData              = gTransmitBuffer;
  transceive.pRxData              = gGarbageBuffer;//gReceiveBuffer;
  transceive.DataSize             = 3;
  transceive.bTxIncrement         = true;
  transceive.bRxIncrement         = false;
  
  adi_GPIO_SetLow(ADI_GPIO_PORT_0,ADI_GPIO_PIN_0);
 
  adi_SPI_MasterTransfer(hDevice, &transceive);
  
  adi_GPIO_SetHigh(ADI_GPIO_PORT_0,ADI_GPIO_PIN_0);
}

And here is my SPI initialization

ADI_SPI_RESULT_TYPE initSPI(void)
{
  ADI_SPI_DEV_ID_TYPE  const devID = ADI_SPI_DEVID_0;
  
  ADI_SPI_RESULT_TYPE Result = ADI_SPI_SUCCESS;  /* assume the best */
  ADI_SPI_DEV_GENERIC_SETTINGS_TYPE settings;
      
    *((volatile uint32_t *)REG_GPIO3_GPCON) |= SPI0_SCLK_PORTP3_MUX
     | SPI0_MISO_PORTP3_MUX | SPI0_MOSI_PORTP3_MUX;// | SPI0_CS_PORTP3_MUX;
    
    /* install and enable DMA error interrupt handeling with OSAL */
   // ADI_INSTALL_HANDLER(DMA_ERR_IRQn, DMA_Err_Int_Handler); // BrJ
   // ADI_ENABLE_INT(DMA_ERR_IRQn); // BrJ
  
  /* Initialize SPI */
    if ((Result =  adi_SPI_MasterInit(devID, &hDevice)) != ADI_SPI_SUCCESS) return Result;
    
    /* configure SPI */
    if ((Result = ConfigureSPI(hDevice)) != ADI_SPI_SUCCESS) return Result;

    if ((Result = adi_SPI_GetGenericSettings(hDevice, &settings)) != ADI_SPI_SUCCESS) return Result;

    return ADI_SPI_SUCCESS;
}


ADI_SPI_RESULT_TYPE ConfigureSPI(ADI_SPI_DEV_HANDLE hSpi)
{
  ADI_SPI_RESULT_TYPE Result = ADI_SPI_SUCCESS;  /* assume the best */
    while (1) {

        /* disable DMA (initially) */ 
        if ((Result = adi_SPI_SetDmaMode(hSpi, false)) != ADI_SPI_SUCCESS) return Result;

        /* set blocking mode so DMA transfers complete without need to poll */
        if ((Result = adi_SPI_SetBlockingMode(hSpi, false)) != ADI_SPI_SUCCESS) return Result;
        
        // Set MSB first 
        if ((Result = adi_SPI_SetLsbFirst(hSpi, false)) != ADI_SPI_SUCCESS) return Result;

        /* send zeros if tx SPI underflows*/
        if ((Result = adi_SPI_SetTransmitUnderflow(hSpi, true)) != ADI_SPI_SUCCESS) return Result;

        /* data transitions on rising edge of clock */
        if ((Result = adi_SPI_SetClockPhase(hSpi, true)) != ADI_SPI_SUCCESS) return Result;
        
        /* data transitions on rising edge of clock */
        if ((Result = adi_SPI_SetClockPolarity(hSpi, false)) != ADI_SPI_SUCCESS) return Result;

        /* run the SST25LF020A up to 1/2 core clock */
        if ((Result = adi_SPI_SetBitrate(hSpi, SPI_CLOCK)) != ADI_SPI_SUCCESS) return Result;
        
        uint32_t freq = adi_SPI_GetBitrate(hSpi);

        /* success */
        return ADI_SPI_SUCCESS;

    } /* end while */
}

I have approximately 10us between each of my 3 bytes I send and 90us between data blocks.

Thank you !