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Grozea.Ion
Grozea.Ion
Associate III
June 20, 2017
Question

STM32F7 USART DMA FIFO example?

  • June 20, 2017
  • 6 replies
  • 1374 views
Posted on June 20, 2017 at 15:29

Hello all,

Does anyone has a USART Rx working with DMA + FIFO in circular mode?

#dma #stm32f7 #fifo #circular-mode
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6 replies

Tesla DeLorean
Tesla DeLorean
Guru
June 20, 2017
Posted on June 20, 2017 at 17:38

I don't see bandwidth being an issue needing to use FIFO mode DMA, it's not an SDIO or DCMI interface delivering >10MBps

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Grozea.Ion
Grozea.IonAuthor
Associate III
June 20, 2017
Posted on June 20, 2017 at 19:31

Hello Clive,

It is not, but as i am learning the F7 i would like to try it.

On the DMA topic...if i remember correctly (i hope my memory is good ) , on the old forum, you had a post for F4 stating that you can trigger a transfer when a

match char

 is detected? I intend to use the DMA for an Xbee communication.

if true, do you still have the link? i tied to find it but i cant or...i'm dreaming

Tesla DeLorean
Tesla DeLorean
Guru
June 20, 2017
Posted on June 20, 2017 at 23:45

The FIFO options represent a handful of additional settings, if you can set up the Circular DMA you'd be 95% the way there.

I don't recall a pattern match method for the USART, you could trigger via a TIM on a periodic basis.

The were some TIM+DMA+GPIO examples outputting pattern-buffers

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AVI-crak
AVI-crak
Senior
July 3, 2017
Posted on July 03, 2017 at 19:11

DMA + FIFO stores / reads the main memory in blocks of 4 bytes or 8 bytes. But the USART can stop reading in one byte. In this case, the data will be lost.

Additionally, in ring mode (DMA_SxNDTR) = 0xFFFF, constantly !!!
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