How to use SSP to GPDMA with linked list?

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How to use SSP to GPDMA with linked list?

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Contributor I

I've download LPC open, there is a sample described how to use GPDMA to move data from SSP0 buffer to RAM without using linked list.

I've test it without linked list, its works.

But I need to do it with linked list.

Can anyone provide a GPDMA sample code with linked list?
Or help me to edit my code, thanks!

#define BUFFER_SIZE (2000)
uint8 Rx_Buf[2][BUFFER_SIZE];
static uint8_t dmaChSSPRx;
static DMA_TransferDescriptor_t gDMADescriptor[2];

Chip_GPDMA_Init(LPC_GPDMA);
NVIC_DisableIRQ(DMA_IRQn);
NVIC_SetPriority(DMA_IRQn, ((0x01 << 3) | 0x01));
NVIC_EnableIRQ(DMA_IRQn);

Chip_SSP_DMA_Enable(LPC_SSP0);

dmaChSSPRx = Chip_GPDMA_GetFreeChannel(LPC_GPDMA, GPDMA_CONN_SSP0_Rx);

Chip_GPDMA_PrepareDescriptor(LPC_GPDMA, &gDMADescriptor[0], GPDMA_CONN_SSP0_Rx, (uint32_t)&Rx_Buf[0][0], BUFFER_SIZE, GPDMA_TRANSFERTYPE_P2M_CONTROLLER_DMA, &gDMADescriptor[1]);

Chip_GPDMA_PrepareDescriptor(LPC_GPDMA, &gDMADescriptor[1], GPDMA_CONN_SSP0_Rx, (uint32_t)&Rx_Buf[1][0], BUFFER_SIZE, GPDMA_TRANSFERTYPE_P2M_CONTROLLER_DMA, &gDMADescriptor[0]);

Chip_GPDMA_SGTransfer(LPC_GPDMA, dmaChSSPRx, &gDMADescriptor[0], GPDMA_TRANSFERTYPE_P2M_CONTROLLER_DMA);

I received GPDMA_STAT_INTERR interrupt after I called Chip_GPDMA_SGTransfer. 

After I check out the register, I found there may be a error in Chip_GPDMA_PrepareDescriptor.

typedef struct DMA_TransferDescriptor {
uint32_t src; /*!< Source address */
uint32_t dst; /*!< Destination address */
uint32_t lli; /*!< Pointer to next descriptor structure */
uint32_t ctrl; /*!< Control word that has transfer size, type etc. */
} DMA_TransferDescriptor_t;

The src is incorrect, it should be GPDMA_CONN_SSP0_Rx not &LPC_SSP0->DR.

This will cause Chip_GPDMA_InitChannelCfg called by Chip_GPDMA_SGTransfer operated incorrect.

Therefore, I've add some code to fix it.

gDMADescriptor[0].src = GPDMA_CONN_SSP0_Rx;

gDMADescriptor[1].src = GPDMA_CONN_SSP0_Rx;

After add this, The first block of Rx_Buf which size is BUFFER_SIZE works fine. But after it finished, DMA_IRQHandler happened constantly by GPDMA_STAT_INTERR

I do not know what I did wrong.

Thank you very much for your assistance.

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NXP Employee
NXP Employee

Hi,

Unfortunately we don’t have an example exactly you need, however you also can refer to the CMSIS library example code.(suppose your device is LPC18xx). You can download it from next  link: https://www.lpcware.com/content/nxpfile/lpc18xx-cmsis-compliant-standard-peripheral-firmware-driver-...

After download it, please check the gdma_linklist.c file located at the path  <lpc18xx_path>/Examples/GPDMA/ Gpdma_Linklist


Have a great day,
Sol

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Contributor IV

Hi @soledad, can I bing to your attention these two posts?
GPDMA library + HSADC and https://community.nxp.com/thread/422356 , they highlight some some difficulties in using LPCOpen and the LPC4370.


Cheers,
Andrea

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Contributor IV

Hi, I don't know ifyou already solved your problem. Anyway, I think that this could be the solution: https://community.nxp.com/thread/422356 
Unfortunately there's a bug in the LPCOpen 2.12 and we have only this workaround as far as I know!

Cheers,
Andrea

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