Accessing data stored in DMA memory by USART

[waleedaslam89]

Posted on July 11, 2012 at 13:55

Hello ,

I am new to STM32. I am reading data from USART using DMA. I dont know how to directly access data from DMA memory after transfer complete interrupt.

[Tesla DeLorean]

Posted on July 11, 2012 at 14:53

Just like any other memory. Use pointers or array access.

If you passed &Buffer to the DMA controller as the transfer address, then Buffer[i]

[waleedaslam89]

Posted on July 12, 2012 at 06:29 The original post was too long to process during our migration. Please click on the provided URL to read the original post. https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I6lD&d=%2Fa%2F0X0000000bum%2F6bueM3fOabdBer.C.5DXX1eBEgsmK3XuJ79ux1PJWFk&asPdf=false

[Tesla DeLorean]

Posted on July 12, 2012 at 11:47

uint8_t *BufferStart = (uint8_t *)0x20004000; // An Address in RAM

uint32_t BufferSize = 10240; .. DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)BufferStart; DMA_InitStructure.DMA_BufferSize = (uint16_t)BufferSize; .. for(i=0; i<BufferSize; i++)  sum += BufferStart[i]; Although I can't see why you couldn't statically allocate the buffer.

[waleedaslam89]

Posted on July 12, 2012 at 12:54

Thanks for your reply,

Actually i am confused in a little bit different manner. For example if I give this Address (e.g 0x20004000) to DMA to start writing from here, and if in my code there are many local functions that create random variables , so is it possible that DMA may corrupt these variables (because DMA only knows the starting address and buffer size ). Pls clarify me in this regard. 

[Tesla DeLorean]

Posted on July 12, 2012 at 15:18

Which is why most of us would statically allocate such buffers, or carve out some space by modifying the linker script or scatter file.