Tearing effect happens randomly after reboot

[JLee.32]

STM32H750 with external flash and SDRAM

TouchGFX version: 4.13.0

CubeIDE version: 1.3.0

display size: 480x272(landscape), but I config the display orientation in portrait in TouchGFX

color depth: 24bits

https://drive.google.com/file/d/1zCucWuLi5BSJUm0VCHaRtqnaUQRpIIhy/view?usp=sharing

Please see the video showing the tearing effect. It happens randomly after reboot. If I reboot 100 times, I can see it around 1~3 times. It will keep exist until next reboot.

I also found setVisibile (left top icon) will cause tearing, but setAlpha (middle icon) will not. Could anyone provide some advice for debugging?

[ktrofimo]

I have seen similar problem ​and it looks like performance issue. Try to minimize number of widgets and check will you have this problem again. Also try to optimize your LTDC timings - may be increase FP and BP to give more time to CPU for drawing, increase SDRAM frequency, move second framebuffer to another bank of SDRAM if you did not it yet...

[JLee.32]

@ktrofimo​ Thank you so much for your advice. It seems that moving seoncd framebuffer to second back of SDRAM works. Will do more test to confirm. Any article describe why we need to do the setting this way?

Also, could you check the video and see if you have other suggestion? You can see some dots are blink around the number 5.

https://drive.google.com/file/d/1KbVwsV9UsbBB2MxYsR6UH7YXY0IubCRC/view?usp=sharing

Regards,

Jimmy

[ktrofimo · Accepted solution]

Take a look at the Application note AN4861 "LCD-TFT display controller (LTDC) on STM32 MCUs" - page 52, section 4.5.3 "Optimizing the LTDC framebuffer fetching from SDRAM" (https://www.st.com/resource/en/application_note/dm00287603-lcdtft-display-controller-ltdc-on-stm32-mcus-stmicroelectronics.pdf)

[JLee.32]

@ktrofimo​ 

Have you seen similar problem for this one? This can not be solved by setting the SDRAM framebuffer address. You can see some pixel around the text "5" are blinking.

https://drive.google.com/file/d/1KbVwsV9UsbBB2MxYsR6UH7YXY0IubCRC/view?usp=sharing

[ktrofimo]

No, have no idea why this happens. How do you draw this "5"? TextArea or Bitmap?​

[JLee.32]

TextArea. Looks like framebuffer 1 and framebuffer 2 have different data since the pixels are blink. These pixels also happen randomly. They can be anywhere around the numbers.