STM32F750 800x480 LCD causing artifacts

MrChips

Joined Oct 2, 2009
30,703
It would seem that the images are consistent, i.e. we are seeing the same pattern. I am going to guess that this is a memory addressing problem and the memory showing the desired colour bars are being written over.

Moreover, it appears to be differences in the colour mapping between the two displays.
 

MrChips

Joined Oct 2, 2009
30,703
480x270 LCD needs 388,800 bytes of graphics memory
800x480 LCD needs 1,152,000 bytes of graphics memory

Is there enough memory allocated for the LCD?
 

Thread Starter

ashkarmalik

Joined Jul 1, 2012
112
It would seem that the images are consistent, i.e. we are seeing the same pattern. I am going to guess that this is a memory addressing problem and the memory showing the desired colour bars are being written over.

Moreover, it appears to be differences in the colour mapping between the two displays.
No Progress till now, Is there any more clue we can work on?
 

chamodabey

Joined Apr 24, 2023
1
What is the problem with this display, I am using the STM32F7508-DK With 800x480 Display but I am getting artifacts when using the transition function in touch gfx

I am using TST070CBOT-01P Along with STM32F7508-DK using RGB Interface , I have wired the jumpers with the display to the corresponding pins and everything works fine in static mode, But when transition begins then the Display shows artifacts as shown in video.

Interface- RGB 24 bits

MCU - 200 MHZ

TFT Clock- 30 MHZ
I also tried to run a 7 inch 800x480 display using STM32F7508-DK board by soldering a breakout board to the FPC pads. But i have the same issue. Issues are only occuring at some change in the screen as mentiond in the replies in the thread. I have posted them int STM forums as follows but unable to got a solution.

https://community.st.com/s/feed/0D53W00002DEuIJSA1
https://community.st.com/s/feed/0D53W00002DVoXsSAL

Then I soldered a breakout board on STM32H750B-DK and then by just doing LTDC parameter changes according to the data sheet to the sample project of H750-DK, I was abled to run the display without any issue. (I did same kind of parameter changes as well as tried varous framebuffer configrations and memory allocation methods in the F750-DK as well, but unable to resolve the issue)

I just add this info because it can be usefull to someone who will be doing same kind of experiments with F750-DK
 

Thread Starter

ashkarmalik

Joined Jul 1, 2012
112
An
I also tried to run a 7 inch 800x480 display using STM32F7508-DK board by soldering a breakout board to the FPC pads. But i have the same issue. Issues are only occuring at some change in the screen as mentiond in the replies in the thread. I have posted them int STM forums as follows but unable to got a solution.

https://community.st.com/s/feed/0D53W00002DEuIJSA1
https://community.st.com/s/feed/0D53W00002DVoXsSAL

Then I soldered a breakout board on STM32H750B-DK and then by just doing LTDC parameter changes according to the data sheet to the sample project of H750-DK, I was abled to run the display without any issue. (I did same kind of parameter changes as well as tried varous framebuffer configrations and memory allocation methods in the F750-DK as well, but unable to resolve the issue)

I just add this info because it can be usefull to someone who will be doing same kind of experiments with F750-DK
Any Update on the solution?
 

Thread Starter

ashkarmalik

Joined Jul 1, 2012
112
Yes. Write your own test code to check that you can access the LCD correctly.
When I am sending a static image (No Animation or Change of graphics) Then there is no problem, But as soon as I start to animate the image or there is image transition there is a scattering of new and old images, and the final image is redrawn correctly.
 

MrChips

Joined Oct 2, 2009
30,703
When I am sending a static image (No Animation or Change of graphics) Then there is no problem, But as soon as I start to animate the image or there is image transition there is a scattering of new and old images, and the final image is redrawn correctly.
That is interesting. Seems like a synchronization or update problem.
What happens if you slow down the animation sequence?
 

John P

Joined Oct 14, 2008
2,025
I don't have an application for a display like this, but it seemed interesting enough to be worth a look. I searched around and found this unit (typically for Chinese vendors, the same thing is available from several of them):
https://www.aliexpress.us/item/2251...!sea!US!2198766673&curPageLogUid=6VkOoNH4tRLp

I hope that monster URL is usable! What that item has as an interface is a 40-pin header; see this image of the back of the display:
https://ae01.alicdn.com/kf/HTB1F_F6tHSYBuNjSspfq6AZCpXad.jpg

I bet they don't include instructions if you buy one, and I can't find data anywhere! What's the likely usage of those connections? I was thinking maybe a Pi Pico could run one of those things without a very complicated interface.
 

Thread Starter

ashkarmalik

Joined Jul 1, 2012
112
That is interesting. Seems like a synchronization or update problem.
What happens if you slow down the animation sequence?
The image update randomly and switches between old and new image block by block.
What I think is the M7 CPU contains Cache Memory which might be causing this problem. Since previously I hav tested the LCD with M4 CPU and it doesn't have cache memory and it works fine.
 

MrChips

Joined Oct 2, 2009
30,703
The image update randomly and switches between old and new image block by block.
What I think is the M7 CPU contains Cache Memory which might be causing this problem. Since previously I hav tested the LCD with M4 CPU and it doesn't have cache memory and it works fine.
What compiler are you using?
Can you disable the cache memory?
 
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