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MK64f12-Twr Spi_dma issues

Question asked by hulaman on Aug 25, 2014
Latest reply on Aug 26, 2014 by Hui_Ma

Hello everyone

I am trying to implement a simple dma based spi code. I started from the edma_dspi demo code from Kinetis SDK1.0.0 and made some changes to suit my application. I am using a dma channel 0, DMATXChannel is from to memory to peripheral.

I am trying to repeatedly send 52 (in hex 0x34) bytes to data through spi0. After setting up the dma, I have the following values on the DMA0 registers

 

  DMA

    DMA_CR = 00000014

    DMA_ES = 00000000

    DMA_ERQ = 00000001

    DMA_EEI = 00000001

    DMA_CEEI = Register is write only

    DMA_SEEI = Register is write only

    DMA_CERQ = Register is write only

    DMA_SERQ = Register is write only

    DMA_CDNE = Register is write only

    DMA_SSRT = Register is write only

    DMA_CERR = Register is write only

    DMA_CINT = Register is write only

    DMA_INT = 00000000

    DMA_ERR = 00000000

    DMA_HRS = 00000000

    DMA_DCHPRI3 = 03

    DMA_DCHPRI2 = 02

    DMA_DCHPRI1 = 01

    DMA_DCHPRI0 = 00

    DMA_DCHPRI7 = 07

    DMA_DCHPRI6 = 06

    DMA_DCHPRI5 = 05

    DMA_DCHPRI4 = 04

    DMA_DCHPRI11 = 0B

    DMA_DCHPRI10 = 0A

    DMA_DCHPRI9 = 09

    DMA_DCHPRI8 = 08

    DMA_DCHPRI15 = 0F

    DMA_DCHPRI14 = 0E

    DMA_DCHPRI13 = 0D

    DMA_DCHPRI12 = 0C

    DMA_TCD0_SADDR = 0000541C (Address of my character array pointer. Yes I checked it and it is the address if the first byte on the array)

      SADDR = 0000541C

    DMA_TCD0_SOFF = 0001

      SOFF = 0001

    DMA_TCD0_ATTR = 0000

      DSIZE = 0

      DMOD = 00

      SSIZE = 000

      SMOD = 0

    DMA_TCD0_NBYTES_MLOFFYES = 00000001

      NBYTES = 001

      MLOFF = 00000

      DMLOE = 0

      SMLOE = 0

    DMA_TCD0_NBYTES_MLOFFNO = 00000001

      NBYTES = 00000001

      DMLOE = 0

      SMLOE = 0

    DMA_TCD0_NBYTES_MLNO = 00000001 

      NBYTES = 00000001

    DMA_TCD0_SLAST = 00000000

    DMA_TCD0_DADDR = 4002C034     (address of SPI_PUSH Register)

      DADDR = 4002C034

    DMA_TCD0_DOFF = 0000

    DMA_TCD0_CITER_ELINKYES = 0034   (MAJOR LOOP COUNT 52 in hex:0x34)

    DMA_TCD1_CITER_ELINKYES = 0000

    DMA_TCD0_CITER_ELINKNO = 0034

      CITER = 0034

      ELINK = 0

    DMA_TCD0_DLASTSGA = 1FFF3980

    DMA_TCD0_CSR = 0012

    DMA_TCD0_BITER_ELINKYES = 0034

    DMA_TCD0_BITER_ELINKNO = 0034

 

If I had set it up correctly, it should have sent 52 bytes and raised an dma complete interrupt. However, what I get is that it sends 8 bytes of data and raises the dma interrupt. It never seems to completely send the data. Can anyone figure out what is set up wrongly based on the register values. Thank you so much for your help.

 

 

Also as a side note, if I put a breakpoint on the callback function that is called upon triggering the interrupt the CITER value is never 0. From what I read in the ref manual, the dma interrupt should be triggered when the value of citer goes to 0. Am I understanding this right.

SPI runs at 10MHz. I have tried it at 1MHZ too but I get the same result.

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