Is it possible to have TouchGFX support XGA (1024 x 768) LCD

[Zli.1]

Hi all,

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I am working on a project that requires a GUI with high resolution. I created a very simple TouchGFX project on a Sharp XGA LCD with a STM32H743 evaluation board. I got glitches between screen transitions. According to ThouchGFX specification, the maximum resolution it supports is 1024 x 720. My questions are, is the glitch caused by the limitation of the resolution? Is it possible to make TouchGFX support higher resolution? Thank you very much.

Zhao Li

[Tesla DeLorean]

Requires a lot of bandwidth, and a lot of memory. Pretty close to the limit on a 2-lane 1-Gbps DSI interface.

Check if the memory implementation is 32-bit wide.

[Zli.1]

Hi Clive1​,

Thank you for your reply. For this test, I am using an official stm32H753Eval board. It does have a 32-bit SDRAM. I have tested the read and write speed of the SDRAM, it can easily go over 150 MB/s with MPU and cache on. I have tried turn on and off the MPU and cache, it does not make any difference. So I think the SDRAM is not the bottle neck. By the way, I am not using a DSI interface, instead, I am using the LTDC port, RGB565 format, and convert the RGB signal to LVDS, which is required by the Sharp LCD screen.

Regards,

[Tesla DeLorean]

The LTDC doesn't use the cache, and does generate a lot of contention.

Probably want to watch the caching / lazy-write / write-buffers on the frame buffer.

Thing to watch on the contention side would be concurrent use of SDMMC interfaces in polled modes.

If you are seeing jitter or tearing on the screen, you'd want to review overall timing/performance, and if multiple frame buffers are appropriate.

What's your refresh rate and pixel clock on the 1024x768 ? Which "Sharp LCD"? Got a specific model number or data-sheet?

[Zli.1]

Hi Clive1,

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Thank you so much for helping me. I am not using a SD or MMC card to store images. I put the images in SPI Flash, and the SPI Flash is running under XIP mode and has been mapped to 0x90000000.

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The LCD I am using is Sharp LQ064X3LW01. The datasheet is in the attachment. And a picture of LTDC settings is also attached.

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I setup a very simple project. I have two screens, each screen has a pictures in the size of 1024x768. And I switch the 2 screens periodically.

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If I set the LTDC clock to 40MHz, the frame rate would be 40,000,000 / (1363 x 802) = 36 Hz. And I can barely see the tearing effect. But because the clock is a lot lower than the recommended frequency, I can see the screen is flickering.

If I increase it to 50Hz, I get a 45 Hz frame rate. The flickering gets weaker, but the trade off is I would see an obvious tearing effect.

Do you have any idea about this? Thanks.

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[Soren Myllerup MIKKELSEN]

Hello Zli.1

In TouchGFX DEsigner you can find an application template for an EDT Smart embedded display module 10,1" running 1024*600.

Maybe you can find some relevant references in this board support package.

[Zli.1]

Hi Soren,

Thanks for your suggestion. I went through their project, but I did not get any inspiration. Their resolution is lower than the maxim resolution (1024 x 700) supported by TouchGFX.

Have you guys every tested Tough GFX with a 1024 x 768 LCD? If it is impossible for TouchGFX support XGA LCDs in the current stage, please let me know. I will make some changes in my project. Thanks.

[Zli.1]

Hi all,

Is there any official people can help and answer my questions? Thank you very much.

[Tesla DeLorean]

Not really, this is primarily a user-to-user forum.

For direct help from ST you should probably be working with your local ST sales/support office, and the FAE (support engineer) for your account situated out of that office. You would need to be a customer of merit to get significant engineering support, ST might be able to provide a list of contractors with specialized experience.

[Zli.1]

Thanks. I will call them.

[JChan.7]

Hello Zli.1

You can check the SDRAM setting , GPIO output speed and HCLK.

[Zli.1]

Hi JChan,

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Thank you for your reply. My SDRAM is working fine. I have already enabled the MPU, so the read and write speed is fast enough to support XGA. I also have tried different LCD pin configuration, making them working under different speed mode. It does not help. As for the HCLK, I slowed don the clock for LTDC to 40MHz, TouchGFX can work with very few tear effect. But because of the clock is a lot lower than the suggested frequency (60Mhz) of the LCD, I can see a few flicker. I have already contact the ST technical support, hope they can give me some suggestions. Thanks.

[Zli.1]

Hi JChan,

Thanks for your answer. Yes, you are right. In my SDRAM settings, I forgot to turn on the burst read. After doing this, the tear effect issue improves. Now my LCD can go with a 66 MHz clock. But along with the increment of the frame rate, I'v got some side effects. Touchgfx is using LTDC clock for the tick event. It seems that the tick event on my board is a lot faster than it was on the simulator. On the simulator, the frequency of tick event is 60 Hz. Plus, the screen transition loses the transition animation.

I am in touch with the ST technical support, hope they can give out some solution. Thanks.