LCD flicker following new FW being flashed

[jchernus-fikst]

Hi all,

I have a screen with an RGB interface (Focus LCD E35KA-FW1000-N) that's being driven by an STM32H747 with the framebuffer in external RAM (over FMC). I'm presently using a double framebuffer strategy, but this same behaviour occurs when I used single.

After flashing new FW, the screen flickers quite badly, and then over a few minutes it settles down and I have a beautiful screen with immediate transitions and no flickering. While it's flickering, you'll see the previous image it was displaying in the background. I'm not too worried about this, it disappears once the flicker is gone.

What could be causing this? 

I can't share the project (under NDA), but I'll gladly answer any relevant questions that can help someone help me solve this. Thanks in advance,

Julia

[GaetanGodart]

Hello @jchernus-fikst ,

Can you share your setup parameter for the screen?
Perhaps your LTDC configurations?

This datasheet : https://www.hpinfotech.ro/ILI9488.pdf tells you some timings to follow :

Is the horizontal synchronization, vertical back porch and DOTCLK Frequency correctly setup?

Regards,

[jchernus-fikst]

Hey @GaetanGodart,

Thanks for responding. Here is the information you asked for:

The values for the first two sections, "Synchronization for Width" and "Synchronization for Height" were provided by Focus LCD. The Signal Polarity I worked out myself.

The DOTCLK frequency is set to 12,307692MHz, which is just above 389 x 507 x 62 = 12.227.826

I believe these all to be within the acceptable bounds. Like I mentioned in my last post - the screen performs wonderfully a few minutes after flashing and has no artifacts during a power cycle. It only happens while flashing.

My problem with this behaviour is that it sticks around for several minutes and looks unprofessional, so I need to fix this before we get this product into the hands of Beta customers. 

Thanks for your help!

Julia

[jchernus-fikst]

Some more settings, in case they're relevant - to avoid going back and forth.

More from LTDC

TouchGFX

DMA2D

Thanks again!

Julia

[jchernus-fikst]

@GaetanGodart any suggestions for how to proceed? Thanks!

[GaetanGodart]

Hello @jchernus-fikst ,

We did not see anything wrong with your implementation.

Maybe the flashing uses some of the pins used for the init.
Can you try to reset your screen after flashing (at the beginning of your application) thanks to the reset signa,l RSX pin, pin 36.

You are un RGB mode right, not MCU mode? (I guess it wouldn't work if in MCU mode)

Could you try to increase a bit your DOTCLK ?

Could you try to run your display with the values in the example?

Once that is done you can check your framerate by checking VSYNC (if using TouchGFX, you can just call a pin VSYNC_FREQ to get it).

Regards,