Abnormal UI happens randomly.

[JLee.32]

HW: STM32H750 with External Flash and SDRAM

Please see the image below, the abnormal UI happens randomly. Could anyone give me some suggestion?

Thanks,

Jimmy

[Alexandre RENOUX]

Hello Jimmy,

Having the image of the issue is great but this will unfortunately not be enough for finding a solution.

Could you tell me what is your setup ? (TouchGFX version, CubeIDE version, display size, color depth, ...)

Here are a few points to look at :

• If you put the text is internal Flash, does it create the same issue (maybe you don't have enough space in internal Flash) ? The idea is to make sure the Flash is not the problem. Also checking with another MCU could confirm the problem is on H750.
• If you have a smaller text, does it trigger the issue ?
• When you run the simulator and press F2*, what are the updated areas ?
• Only texts have the problem or images too ?

(* Fixed typo from F12 to F2)

/Alexandre

[JLee.32]

Hi Alexandre,

Thanks for your reply. Please see my partial answers below.

Also, I tried to reduce FMC(SDRAM) clock from 200M to 120M, and the abnormal is gone, but for 80M and 64M, the display went chaos. Thus, only 120M is okay.

I haven't tested EMC and RA. Mabye FMC clock needs to be fine tune in the future, so I hope 120M is not the only solution. Do you have any thought on this?

TouchGFX version: 4.13.0

CubeIDE version:

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

color depth: 24bits

• If you have a smaller text, does it trigger the issue ?

haven't found the issue with smaller text so far. Maybe it's not obvious to observerd.

• When you run the simulator and press F12, what are the updated areas ?

Do you mean F2? The invalidate area is around the texts.

• Only texts have the problem or images too 

Only texts.

Regards,

Jimmy

[Alexandre RENOUX]

Hello Jimmy,

Tweaking the clock speed of the display interface or the RAM speed is a common thing to do.

For the reason behind it, I don't know exactly but I will keep that in mind to investigate.

But as a first guess, I would say that it's because of desynchronization. basically if your SDRAM is too fast for the MCU and display or too slow, you can experience this kind of things. It's important to find the right spot usually. In general, clock speed is always something to look at when Tearing is involved.

Having big texts, by experience, often leads to this tearing effect, But more broadly, there's always a bigger chance of tearing when you have a big widget invalidated, than a small one because the number of pixels to compute and update are drastically different. Text also has alpha included which increases the load.

Yes I meant F2, sorry for the typo ^^'

/Alexandre

[JLee.32]

@Alexandre RENOUX​ 

Hi Alexandre,

Could you take a look this thread and give me some suggestion?

https://community.st.com/s/question/0D53W00000uZEIxSAO/textarea-shows-extra-pixels-randomly

Thanks,

Jimmy