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a_pradyumna
a_pradyumna
Associate
October 12, 2016
Question

Restarting DMA with new configuration

  • October 12, 2016
  • 2 replies
  • 2027 views
Posted on October 12, 2016 at 12:45

Hello,

I am using STM32F030x. I am trying to read the data from the UART using DMA (channel 2 -> Tx and channel 3-> Rx ). I used CubeMx to generate the initial code and configuration. The DMA is configured in NORMAL mode. 

I use HAL_UART_Receive_DMA() to start and receive the data on the UART.

Now, I have to collect the data into another memory location after a certain time while the initial transfer is not complete. To do this I stop the DMA using HAL_UART_DMAStop() and re-enable the new transmission using HAL_UART_Receive_DMA() . 

The problem I am facing is that between this HAL_UART_DMAStop and HAL_UART_Receive_DMA, the chip is taking too much time and I am loosing data which is coming on the UART.

I would like to know if there is another way to reconfigure the DMA memory register and Size without stopping the DMA or in the fastest way possible.

#stm32 #dma
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2 replies

Walid FTITI_O
Walid FTITI_O
Visitor II
October 12, 2016
Posted on October 12, 2016 at 13:50

Hi , 

The recommendations in the application note

http://www.st.com/content/ccc/resource/technical/document/application_note/27/46/7c/ea/2d/91/40/a9/DM00046011.pdf/files/DM00046011.pdf/jcr:content/translations/en.DM00046011.pdf

would be hlpful for you:

''

 

4.1 Software sequence to disable DMA

 

To switch off a peripheral connected to a DMA stream request, it is mandatory to:1. switch off the DMA stream to which the peripheral is connected,2. wait until the EN bit in DMA_SxCR register is reset (“0�).Only then can the peripheral be safely disabled. DMA request enable bit in the peripheralcontrol register should be reset (''0'') to guarantee that any pending request from peripheralside is cleared.Note: In both cases, a Transfer Complete Interrupt Flag (TCIF in DMA_LISR or DMA_HISR) is setto indicate the end of transfer due to the stream disable.

 

4.2 DMA flag management before enabling a new transfer

 

Before enabling a new transfer, the user must ensure that the Transfer Complete InterruptFlag (TCIF) in DMA_LISR or DMA_HISR is cleared.As a general recommendation, it is advised to clear all flags in the DMA_LIFCR andDMA_HIFCR registers before starting a new transfer.

 

4.3 Software sequence to enable DMA

 

The following software sequence applies when enabling DMA:1. Configure the suitable DMA stream.2. Enable the DMA stream used (set the EN bit in the DMA_SxCR register).3. Enable the peripheral used. DMA request enable bit in the peripheral control registershould be set (''1'').

 

Note: If the user enables the used peripheral before the corresponding DMA stream, a “FEIFâ€�(FIFO Error Interrupt Flag) may be set due to the fact the DMA is not ready to provide the first required data to the peripheral (in case of memory-to-peripheral transfer).

 

''

 

-Hannibal-

a_pradyumna
a_pradyumnaAuthor
Associate
October 13, 2016
Posted on October 13, 2016 at 17:11

Thank you very much for your reply and information.

I managed to reconfigure using : 

__HAL_DMA_DISABLE(huart1.hdmarx);
while
((huart1.hdmarx->Instance->CCR & DMA_CCR_EN) != 0);
huart1.hdmarx->Instance->CMAR = <New Address>
huart1.hdmarx->Instance->CNDTR = <New size>
__HAL_DMA_ENABLE(huart1.hdmarx);

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