Skip to main content
LeonidP
Associate II
March 16, 2025
Solved

DAC in DMA mode @ enabled cache

  • March 16, 2025
  • 3 replies
  • 664 views

Hello!

 

A simple question. 

If I run DAC, using HAL_ADCEx_MultiModeStart_DMA(..., buffer, ...), when D-cache is disabled, I succeed to send what I filled in the buffer. 

If I do the same with enabled D-cache, I don't succeed. 

SCB_InvalidateDCache_by_Addr() function, which is useful in ADC callbacks, seems to be not helpful for DAC.

 

How to fix that?

 

This topic has been closed for replies.
Best answer by ahsrabrifat

Use SCB_CleanDCache_by_Addr() Before Enabling DMA

Before starting the DAC DMA transfer, call:

 

SCB_CleanDCache_by_Addr((uint32_t*)buffer, buffer_size);

 

where:

  • buffer is the pointer to your DAC buffer.
  • buffer_size is the number of bytes in the buffer.

3 replies

ahsrabrifatBest answer
Senior III
March 16, 2025

Use SCB_CleanDCache_by_Addr() Before Enabling DMA

Before starting the DAC DMA transfer, call:

 

SCB_CleanDCache_by_Addr((uint32_t*)buffer, buffer_size);

 

where:

  • buffer is the pointer to your DAC buffer.
  • buffer_size is the number of bytes in the buffer.
    Tesla DeLorean
    Tesla DeLorean
    Guru
    March 16, 2025

    The command to FLUSH the pending memory for a DMA (memory-to-peripheral) is SCB_CleanDCache_by_Addr()

    The SCB_InvalidateDCache_by_Addr() throws away the pending/dirty cache content, ie stuff you've created in the buffer. It's what you'd use when DMA (peripheral-to-memory) has changed the underlying content of the memory

     

    Remember that the by_Addr() expects 32-byte alignment buffers and sizes. You need to add guard zones around the buffers if you can't do that, the Invalidate can do collateral damage.

    Tips, Buy me a coffee, or three.. PayPal Venmo (See Profile) Up vote any posts that you find helpful, it shows what's working..
      LeonidPAuthor
      Associate II
      March 17, 2025

      Thanks. With SCB_CleanDCache_by_Addr() it works.

      Terms & ConditionsAccessibility statement