STM32H723 DMA works well, but after i copy the data which dma wrote, dma doesnt work anymore.

[Dongdongguri]

Hi, thanks for reading my question.

I use DMA for ADC, and it works well, one shot mode, and starts gain, data changed well from the ADC.

But, if I read the data, then DMA works but it cant write it into the memory.

#define MAX_DMA_MEMORY_SIZE	2552

ALIGN_32BYTES (static uint8_t ADC_DMAMemory[MAX_DMA_MEMORY_SIZE]);

HAL_ADC_Start_DMA(&hadc1, (uint32_t *) ADC_DMAMemory, MAX_DMA_MEMORY_SIZE);

 and just copy the data 1 time

    	for(int i = 0; i < nsize; i++)
    	{
    		pVal[i] =  ADC_DMAMemory[i+ioffset];
    	}

I use dma for 2552 data, and copy 2048 data to pVal. So just copied 389th array to 2437th.

and after this copy, DMA refresh only 0 to 384th, and 2438 to 2552. 

DMA never write data to the address where i copied.

if i dont copy data, it works well, every time, it writes new data.

Please help me, i just went through H7 weird data cache usage, and i met another problem.

Thanks in advance.

[FBL · Accepted solution]

Hello @Dongdongguri 

First try to disable the cache and see if the issue disappears. If so, you should maintain data cache coherency. 

[Dongdongguri]

thanks, i thought i tested it, but i didnt.

below is working now.

void HAL_ADC_ConvHalfCpltCallback(ADC_HandleTypeDef *hadc)
{
	SCB_InvalidateDCache_by_Addr((uint32_t*) &ADC_DMAMemory[0], 2552/2);
	memcpy(&ppiVal[0], &ADC_DMAMemory[0], MAX_DMA_MEMORY_SIZE/2);
}

[Piranha]

That is not enough. The size of every half-buffer must be a multiple of the cache line size. And the buffers must be invalidated before and after the DMA reception.

https://community.st.com/t5/stm32-mcus-products/maintaining-cpu-data-cache-coherence-for-dma-buffers/m-p/95746

[Dongdongguri]

So i have 2 choice, invalidate it before and after the DMA, or just using Link script to make 0x30000000 to use DMA memory, i tested 0x30000000 to 0x30000200, it works. and I will use LAN too. maybe i can use next address for this. then all problem will be solved.

Thank you.