STM32H743 LTDC Display Flickering Issue with LI10600T070IA3098-TCF

[Mukeshkanna]

Hello,

We are using an STM32H743 MCU with the LI10600T070IA3098-TCF LCD panel (1024×600 resolution) through a 24-bit RGB LTDC interface. We are experiencing display flickering, as shown in the attached video.

Could you please help us identify the possible root cause? Kindly let us know what additional information (schematic, LTDC timing parameters, oscilloscope captures, PCB layout, etc.) would be required from our side to assist in debugging this issue.

Any guidance or recommendations would be greatly appreciated.

https://drive.google.com/file/d/1wClnXqdIc8OI-4y19CmWxJERnSnIYUK-/view?usp=sharing

 

[mƎALLEm]

Hello ​@Mukeshkanna and welcome to the ST community,

1- Sorry I can’t open a link from google drive. Meanwhile LCD flickering could be due to a Cortex-M7 speculative access to a non valid external memory region. Please refer to this knowledge base article: Speculative access on Cortex®-M7 and Cortex®-M85 based STM32: A practical guide

2- For the LTDC configuration and timings you can refer to the application note: AN4861 “Introduction to LCD-TFT display controller (LTDC) for STM32 MCUs”

[Mukeshkanna]

Hello @m3ALLEm,

Thank you for your response and suggestions.

Please find a video of the issue below:

https://youtube.com/shorts/5WoL0AP-tDQ

 

In our design, the display is interfaced to the STM32H743 through the LTDC RGB interface. The framebuffer is stored in external SDRAM connected through FMC.

Could you please review the attached video and let us know if the observed behavior could be related to Cortex-M7 speculative access or MPU/cache configuration? If so, could you kindly suggest the recommended MPU and cache settings for LTDC applications using external SDRAM as the framebuffer?

We will also review AN4861 and the knowledge base article you shared.

Thank you for your support.

Best Regards,
Mukesh

[mƎALLEm]

Hello,

I’m not LTDC interface expert. As I said please check your MPU configuration and disable the access to all unused memory regions.

That’s not related to the frame buffer cachability but (perhaps) to a speculative behavior of the Cortex-M7 to non valid memory regions. Did you read the article I shared?

[jumman_JHINGA]

It's looking like you have selected high LTDC frequency in the clock configuration. And your LTDC parameters are not matching to that frequency.  Check yours display's data sheet and set LTDC parameters accordingly or try to reduce LTDC frequency. 

[Mukeshkanna]

Hello ​@jumman_JHINGA ,

Thank you for your suggestion.

For your reference, I have attached an Excel document containing the complete LTDC configuration, timing parameters, and clock configuration currently used in our design.

Could you please review the attached settings and let us know if you observe any mismatch between the LTDC timings, pixel clock frequency, and the LCD panel requirements that could potentially cause the display flickering issue?

Any recommendations or observations would be greatly appreciated.

Thank you for your support.

[jumman_JHINGA]

hii ​@Mukeshkanna 
i have gone through with your configuration file and compared these parameter with yours display datasheet.. yours Horizontal Timing looking correct. but in the Synchronization for Height section Total Height is 769  .. nut according to data sheet it should be in between 624~750 ….instead of VFP = 127 try VFP  =  12 or VFP = 1 that would give you Total Height = 655 or 644 that lies comfortably inside the datasheet limits.

and second thing is LTDC clock. according to the  datasheet your display supports Min :40.8 MHz, Typical : 51.2 MHz and Maximum 67.2 MHz . You should verify CubeMX is generating an LTDC clock inside this range. 

and one more important thing  yours CubeMX report shows:

• CPU I-Cache = Disabled
• CPU D-Cache = Disabled

This won't prevent the display from working, but for a TouchGFX application on an STM32H743, it's unusual. Once basic display operation is confirmed, enabling the caches (with proper MPU configuration) will significantly improve graphics performance.

 

[Mukeshkanna]

Hi ​@jumman_JHINGA 

Thank you for your suggestions.

We have verified the recommended parameters and carried out the suggested modifications.

• We changed the Vertical Front Porch (VFP) to 12 and 1, bringing the Total Height within the datasheet-specified range. However, the display behavior remained unchanged, and the flickering issue still persists.
• We also verified the LTDC clock and ensured that it is configured within the display datasheet's supported range (40.8 MHz to 67.2 MHz). This also did not result in any improvement.
• Additionally, we enabled both CPU I-Cache and CPU D-Cache with the appropriate configuration. However, there was no noticeable change in the display flickering.

The flicker is still present and appears as a wave moving from the top of the display to the bottom. It is more noticeable with certain colors and less visible with others.

Please let us know if there are any other parameters or hardware-related checks that you would recommend.

Thanks,
Mukesh