STM32H7: Screen Flickering, Missing Text, Mixed Screens During Navigation

[Mehulrana511]

STM32H7S78 

Software:

TouchGFX Designer + STM32CubeMX + STM32CubeIDE

Problems observed:

- Screen flickers randomly especially during screen transitions.

- UI text disappears or becomes invisible after returning to a screen.

- Mixed or corrupted screens — elements from previous screen appear on the next one.

- Sometimes partial or outdated frame buffer content is displayed.

These issues occur consistently when navigating between screens, I attached video for your reference.

TouchGFX Environment:

- LTDC enabled, RGB interface, external display 7” TFT

- TouchGFX task priority: Normal

- TouchGFX task stack size: 4096 bytes

- Running under FreeRTOS

What I have already tried:

- I have tested the following but issue still persists:

- Increased TouchGFX task stack (4096 → 8192)

- Ensured LTDC clocks are correct

- Ensured invalidate() is called after UI updates

Looking forward to your further guidance.

Best regards,

Mehul Rana

[mƎALLEm]

Hello,

Ensure first you activated the default MPU configuration to prevent CM7 speculative access for invalid memories,

Then you need to enable the MPUs for the external memeories you are using.

Unfortunately we cannot download your attachment it's blocking by a Virus scanning step: Attachments stuck on "virus scan in progress..."

[Mehulrana511]

Hello,

Thank you  for your guidance.

As suggested, I have enabled the default MPU configuration, and I have also added MPU regions for the external memories used by TouchGFX, but problem remains even after enabling MPU.

Below I am attaching:

- CubeMX MPU configuration screenshot

- My full MPU_Config() code

- A video link demonstrating the flicker / corrupted-screen issue

/* MPU Configuration */

static void MPU_Config(void)
{
  MPU_Region_InitTypeDef MPU_InitStruct = {0};

  /* Disables the MPU */
  HAL_MPU_Disable();

  /** Initializes and configures the Region and the memory to be protected
  */
  MPU_InitStruct.Enable = MPU_REGION_ENABLE;
  MPU_InitStruct.Number = MPU_REGION_NUMBER0;
  MPU_InitStruct.BaseAddress = 0x0;
  MPU_InitStruct.Size = MPU_REGION_SIZE_32KB;
  MPU_InitStruct.SubRegionDisable = 0x87;
  MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;
  MPU_InitStruct.AccessPermission = MPU_REGION_NO_ACCESS;
  MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_DISABLE;
  MPU_InitStruct.IsShareable = MPU_ACCESS_SHAREABLE;
  MPU_InitStruct.IsCacheable = MPU_ACCESS_NOT_CACHEABLE;
  MPU_InitStruct.IsBufferable = MPU_ACCESS_NOT_BUFFERABLE;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);

  /** Initializes and configures the Region and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER1;
  MPU_InitStruct.BaseAddress = 0x20000000;
  MPU_InitStruct.Size = MPU_REGION_SIZE_64KB;
  MPU_InitStruct.SubRegionDisable = 0x0;
  MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL1;
  MPU_InitStruct.AccessPermission = MPU_REGION_FULL_ACCESS;
  MPU_InitStruct.IsShareable = MPU_ACCESS_NOT_SHAREABLE;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);

  /** Initializes and configures the Region and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER2;
  MPU_InitStruct.BaseAddress = 0x70000000;
  MPU_InitStruct.Size = MPU_REGION_SIZE_64MB;
  MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_ENABLE;
  MPU_InitStruct.IsCacheable = MPU_ACCESS_CACHEABLE;
  MPU_InitStruct.IsBufferable = MPU_ACCESS_BUFFERABLE;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);

  /** Initializes and configures the Region and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER3;
  MPU_InitStruct.BaseAddress = 0x90000000;
  MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_DISABLE;
  MPU_InitStruct.IsCacheable = MPU_ACCESS_NOT_CACHEABLE;
  MPU_InitStruct.IsBufferable = MPU_ACCESS_NOT_BUFFERABLE;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);

  /** Initializes and configures the Region and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER4;
  MPU_InitStruct.BaseAddress = 0x24000000;
  MPU_InitStruct.Size = MPU_REGION_SIZE_128KB;
  MPU_InitStruct.IsShareable = MPU_ACCESS_SHAREABLE;
  MPU_InitStruct.IsCacheable = MPU_ACCESS_CACHEABLE;
  MPU_InitStruct.IsBufferable = MPU_ACCESS_BUFFERABLE;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);

  /** Initializes and configures the Region and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER5;
  MPU_InitStruct.BaseAddress = 0x24068000;
  MPU_InitStruct.Size = MPU_REGION_SIZE_16KB;
  MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;
  MPU_InitStruct.IsShareable = MPU_ACCESS_NOT_SHAREABLE;
  MPU_InitStruct.IsCacheable = MPU_ACCESS_NOT_CACHEABLE;
  MPU_InitStruct.IsBufferable = MPU_ACCESS_NOT_BUFFERABLE;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);
  /* Enables the MPU */
  HAL_MPU_Enable(MPU_PRIVILEGED_DEFAULT);

}

Video Link:

TouchGFX Screen Video 

I appreciate your continuous support and guidance.

Thank you.

Best regards,

Mehul Rana