Flickering on STM32H755 with alpha effects on images

[FBena.1]

Hi everyone,

I have the following "flickering" problem using TouchGFX with an STM32H755 board. The problem occurs when performing a "fade in" effect by varying the alpha of an image from 0 to 255 in a certain time.

Everything else seems to work fine, but the problem only occurs when I apply alpha transitions to images.

At the moment I'm experimenting with DMA2D Input Color mode L8.

Below you can find all the settings used.

What do you think is the problem?

Thanks to all those who want to contribute to the discussion.

VIDEO OF THE ISSUE

https://drive.google.com/file/d/160AH0cQSda6t6FoSJ-u-yQKXbn7Dx5vw/view?usp=sharing

CONFIGURATION

TouchGFX

 

DMA2D

 

LTDC

 

 

CLOCK

 

[Alexandre RENOUX]

Hello FBena.1,

​

The first thing to confirm is : does it only happen with L8 ? In order to check, use RGB565 for instance and see if you also have flickering. If not then it's the L8 usage that causes the problem and in this case we can investigate further in that direction ;)

/Alexandre

[FBena.1]

Hi Alexandre,

thanks for your interest in topic.

Yes I confirm that it happens only with L8. In case of RGB565 the alpha fade effect works perfectly.

Additionally i'm using TouchGFX 4.18.1 and STM32CubeIDE 1.8.0.

Best regards

[Alexandre RENOUX]

Hello FBena.1,

Ok now we need to try on a different board and check if this happens also with other boards or if it is only your specific hardware that creates this effect. If it works just fine on other boards, then I believe your hardware config is wrong.

If not, this is definitely a global issue from TouchGFX and we will try to fix it as soon as possible.

I'll investigate on my side.

Best regards,

Alexandre

[FBena.1]

Thanks for the feedback.

If you need more information on my sw or hw configuration let me know.

[Alexandre RENOUX]

Hello FBena.1,

After looking a bit more closely at your configuration screenshots. I clearly see a problem.

Your color depth format is not consistent.

L8 images are used to save memory but the framebuffer format should not be L8.

Please set everything like you would for RGB565 and you just set the image in the Designer as L8_RGB565 ou L8_ARGB8888 if you want alpha included.

Please refer to the Documentation website

/Alexandre