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Problem with DMA and SPI

 
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meca90



Joined: 06 Apr 2014
Posts: 6

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Problem with DMA and SPI
PostPosted: Mon May 25, 2015 11:44 pm     Reply with quote
Hi, I'm trying to use the DMA with SPI and SD Card, what I'm doing is simply replacing the SPI_WRITE and SPI_READ library functions that use for memory, instead DMA variables but it does not work that way, I'm missing something? I think I should mimic the structure SPI_READ() and SPI_WRITE() functions, to complete the process well. [I have had successful results with other DMA modules like PWM, ADC, UART]

For example i try to replace this
Code:

   for( i=0;i<16;i++){
      spi_write(0xff);
   }


For this
Code:

 for( i=0;i<16;i++){
      CHEN3=1;
      SPI1TX=0xFF;
      FORCE3=1;
}

PD: here this code settings of SPI with DMA, and use the microcontroller DSPIC33EP256MU806
Thanks
best regards.
Code:

   setup_dma(3,DMA_OUT_SPI1,DMA_BYTE);                           
   dma_start(3,DMA_ONE_SHOT|DMA_NO_INC|DMA_FORCE_NOW ,&SPI1TX);                   

   setup_dma(4,DMA_IN_SPI1,DMA_BYTE);
   dma_start(4,DMA_ONE_SHOT|DMA_NO_INC|DMA_FORCE_NOW,&SPI1RX);

Send a Byte:
      CHEN3=1;
      SPI1TX=0xFF;
      FORCE3=1;

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