Many error pixels on screen!

[imarz.1]

I got the STM32H747I-DISCO Discovery kit, and I made screen with just two buttons. On the gfx simulator, everything is fine, but as you can see on attached picture, on the real LCD I see so many error pixels both around the buttons, and diagonally. I suspect it is in the setting of the LCD in the Cube ide. The datasheet for the LCD lacks HW details(Horizontal/Vertical Front/Back Porch, VSync/HSync Width etc.), so I am using the defaults.

It also maybe the LCD clock. It is set now at 38MHz. Not sure what is the correct clk setting.

If anyone have any idea, please let me know.

PS: I am using Touchgfx 4.19.0, and Cube ide 1.9.0

Thanks.

[Yoann KLEIN]

Hello @imarz.1​ ,

I tried to reproduce your error, but everything works fine for me.

Can you please follow these steps to ensure that the issue comes from your display and not from something else :

• In TouchGFXDesigner, set your background color at perfect red, like this :

• In CubeIDE, put a breakpoint in the function HAL_DSI_TearingEffectCallback() in TouchGFXHAL.cpp, click on Window>Show View>Memory, and then select your framebuffer address to see if a pixel in the first row is different from red (FF0000).

 

Thanks,

/Yoann

[imarz.1]

Hello,

I just debugged it, and I got exactly the same numbers as yours.

Also, the demo board is brand new. I got it last week.

So, I did not really write any code. I just created two buttons in Touchgfx, and then through Cube ide I programmed it to the demo board. Everything is default.

[Tesla DeLorean]

Surely the BSP example code for the platform exposes the timings, perhaps review those?

[Jnevi.1]

hmm, i have a similar error (maybe)

I'm using a BW display and this is what i get in the simulator with a progress bar. There pixel errors

[Jnevi.1]

and these pixel errors i also get on the display

[Jnevi.1]

any update on this? as i have these errors in the simulator aswell i think it is a touchgfx related error

[imarz.1]

It is fixed by programming the board from within the Touchgfx studio at least once. I initially did not do that. I was making the GUI changes in the Touchgfx studio, saving the project, then I would go to the CubeIDE, and program the board from there.

I do not know what is the difference between the two, but it magically fixed the issue, and I have never seen it again.

Also, the long programming time problem is gone after I re-started the PC. Maybe the PC was in some unstable state. Not sure why. I only had CubeIDE, and Touchgfx studio open at that time.

This is why I recommend they merge the Touchgfx studio with the Cube IDE. Make them one application just like Visual studio has GUI resource editor within the Visual studio itself. This might eliminate many weird issues like these.

[Jnevi.1]

ok, i found the solution for the error shown in the screenshot above

It has something to do with the dither algorithm. If i change the algorithm i get others pixel errors. if i disable dithering no pixel errors

I got currious because i had the errors in the simulator aswell so it had to be some problem of touchgfx and not the simulator

so these pixel errors may a) be unreleated and in other cases it may be some hardwarre error

b) 1-bit B/W mode seems to trigger some of these effects