Chopping occuring on STM32F769-Disco

Question

Hi,

I am running a simple GUI using code from established projects on the STM32F769-Disco and am getting chopping (see picture) on boot and when scrolling a vertical list.

I have tried double buffer but no improvement.

Any ideas? This is using V11.00.01.

Thanks

Phil

 

Answer 1

Hi Phil,

this seems to me that some display settings are not correctly. Is the chopping statically or somehow jittering or different after each update?

Just to have a common understanding - please try the following:

You are using theSTM32F769-Discovery board and the suitable Build Environment, correct?

Build HelloWorld and some of the other provided examples from the Build Environment - are they working correctly?

Now you can generate the code of your existing GUI project (ScreenSize = 800x480) into the folder /GeneratedCode and build the binary as the other examples. Then the chopping appears?

Best regards,

Manfred

Comments

Hi Manfred,

I am using the Build Environment zip files from the our get.embedded... ftp area, the only difference is I have applied our RGB888 files.

The examples build and run fine (Paper cutter and washing machine) and I am doing exactly what you decribed above, I am building into the same Generated Code folder as the demos and building and programming the same way.

It seems the vertical list is most affected.

Thanks

Phil

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Hi Phil,

are there any messages on the console?

Does the jitter appears only sometimes? Then it seems to be some buffer underflow,

Best regards,

Manfred.

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Hi Manfred,

Yes, the jitter is not consistent, and self recovers on the next change.

No errors are shown on the debug unfortunately.

Best Regards

Phil

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Hi Phil,

I can reproduce the same jitter effect by using the WashingMachine example and changing the ColorFormat to RGB888. Further investigations are ongoing. I keep you informed...

How urgent is this issue for you? Can you continue with RGB565 instead?

Thanks for reporting the issue.

Best regards,

Manfred.

Answer 2

Hi Phil,

the jittering is caused by the alignment of the framebuffer, which has to be a multiple of 64 bytes in order to satisfy the LTDC. In case of color format RGB888 and a framebuffer width of 800 pixel this is not fulfilled. The framebuffer has to be adjusted to 832 pixel and the DSI update has to be adjusted accordingly. For more details, let me recommend the AN4861 from ST - there you will find some additional information to optimize the SDRAM access and LTDC configuration.

Please download this small patch for the Build Environment for STM32F769-Discovery board (V11.00.01).

Please note, there is no need to change the ScreenSize within your GUI project.

Let me know if this works for your application.

Best regards,

Manfred.

Comments

Hi Manfred,

Yes, that has solved the issue. Thanks for your help.