DMA request generation on STM32H7

HansPLJ · ‎2024-02-04

Hi!

I am looking into the possibility on using LPTIM1 to trigger a DMA transfer with no CPU interrupt. This timer is chosen because it can be clocked directly by the HSE clock input. In the datasheet of STM32H7B3 (DS13139 - Rev 8) table 4, it states that LPTIM1 cannot be used for DMA request generation. In table 103 in the reference manual (RM0455 Rev 11) lptim1_out is listed as as a resource.

Does this mean that it is not possible to use an output from LPTIM1 directly as an DMA request generator, but it is possible when using the DMA mux?

Any clarification would be appreciated!

FBL · ‎2024-02-05

Hello @HansPLJ

It is not possible to use directly DMA request generation. However, you can use it through DMAMUX. Your interpretation is correct. By using a DMAMUX, you can dynamically switch the DMA channels source based on your system's requirements at any given time. This allows for more efficient use of the available DMA channels and greater flexibility in your system design.

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LCE · ‎2024-02-05

I don't know that H7 / LPTIM. Check the LPTIM CR / IE registers, is there any "DMA enable" bit?

FBL · ‎2024-02-05

Hello @HansPLJ

It is not possible to use directly DMA request generation. However, you can use it through DMAMUX. Your interpretation is correct. By using a DMAMUX, you can dynamically switch the DMA channels source based on your system's requirements at any given time. This allows for more efficient use of the available DMA channels and greater flexibility in your system design.

To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

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Happy New Year!

HansPLJ · ‎2024-02-05

Thank you for the clarification!

SofLit · ‎2024-02-05

Refer also to the AN5224 "STM32 DMAMUX: the DMA request router"

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