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Claydonkey
Associate III
May 21, 2023
Question

Is it possible to update more than 1 DMA stream on the TIMx_UP DMA request (STM32H7B0)

  • May 21, 2023
  • 9 replies
  • 1988 views

Is it possible to update more than 1 DMA stream on a "timer up" DMA request (TIMx_UP)?

I am using an STM32H7B0 with the HAL library and can initialize and start the timer/dma interrupt for one DMA request but can more be introduced for the TIMx_UP interrupt?

DMA_HandleTypeDef hdma_timx_up; 
hdma_timx_up.Instance = DMAx_Streamx.
...
HAL_DMA_Init(&hdma_timx_up)
 

start (for GPIO toggling)

HAL_DMA_Start_IT(htimx.hdma[TIM_DMA_ID_UPDATE], (uint32_t) dmaarray, (uint32_t) &(GPIOx->BSRR), dmalen);

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9 replies

waclawek.jan
waclawek.jan
Super User
May 21, 2023

No.


_legacyfs_online_stmicro_images_0693W00000bkVHrQAM.png 

The underlying reason is, that for some peripherals - including TIM - the DMA request goes through a latch, which is reset by the DMA/DMAMUX when the request is served. In other words, the first channel which serves the given request clears the latch, with unpredictable results to the second channel connected to the same request. In 'F4, this leads to one of the DMA streams to be frozen entirely (guess how do I know :) ); with DMAMUX the results may be different, but the above warning in the RM indicates, that this is simply something which is not to be attempted.

JW

ClaydonkeyAuthor
Associate III
May 22, 2023

Thank JW.

I will use multiple timers then.

However can you use the dma_generator to create multiple dma streams that fire on and timup interrupt?

waclawek.jan
waclawek.jan
Super User
May 22, 2023

I'm not sure what do you mean by dma_generator.

In DMAMUX, individual channels can generate events (dmamux_evt, DMAMUX_CxCR.EGE, and some of the events can be selected as triggers to the DMAMUX's Request generator. That supposedly allows to chain DMAMUX channels, and thus generate a chain of requests for several DMA channels/streams. However, I don't use any STM32 with DMAMUX so don't know the intimate details of this.

JW

AScha.3
AScha.3
Super User
May 22, 2023

( i dont use DMAMUX also )

but seems possible on H7:


_legacyfs_online_stmicro_images_0693W00000bkZULQA2.png

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waclawek.jan
waclawek.jan
Super User
May 22, 2023

That just means, that you can use any DMAMUX channel for any request, not that you can use several DMAMUX channels at the same time for the same request. See the RM screenshot I gave above.

JW

AScha.3
AScha.3
Super User
May 23, 2023

Thx, Jan , just the "in parallel to all channels" has seduced me to think, maybe...

(because: if in this DMAMUX-thing every out channel has its own state (Flip-Flop (?)) ,

DMA request / DMA served , then it would be possible , as long as only one serves the orignal request source and other just do a mem to mem transfer - or whatever . )

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Tesla DeLorean
Tesla DeLorean
Guru
May 23, 2023

Could one use CCRx = 0 triggers as secondary, tertiary proxies for UPDATE trigger? Phase alignment here would be simpler than using multiple timers and synchronizing them.

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waclawek.jan
waclawek.jan
Super User
May 23, 2023

Just as a curiosity, in the 'H7Ax/7Bx, TIM4_CH4 is not connected to DMAMUX1 requests.

JW

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