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Pixel computation issue

Plaramee
Associate III

Hi all, I'm running into an issue and I need some ideas!

We have designed a project on a STM32T769 disco board and we are now porting it onto our own hardware that uses an STM32H743 chip. We have 64MB of external SDRAM (two chips of 32MB each running in parallel) and a parallel LCD display. All code runs from internal flash and for this part (the bootloader), all assets of TouchGFX are also in internal flash.

We are seeing weird pixels on our display. I attached an image. Basically, some lines close to the squares are the wrong color. Look at the lower right blue square, it has a black line on the left. The text is also quite blurry. As if some calculations were wrong. I was able to see the these wrong pixels are actually into the frame buffer in SDRAM so it is not a LCD timing issue.

It seems to be related to computations made for overlapping objects as if I only have one color box, I see no issues.

Any body has ideas on what to look for when facing this kind of problem?

Thanks in advance.

4 REPLIES 4
Martin KJELDSEN
Chief III

Hi @Philippe Laramée​,

I don't expect this issue to be in your simulator? I can see the text is pretty blurry, yeah.

/Martin

Plaramee
Associate III

The exact same GUI was working fine on the STM32F769 Disco board so it is not GUI related, it is something with the new CPU, SDRAM or configuration... This is what I am trying to figure out.

Plaramee
Associate III

Well it turns out we had a hardware issue with two control pins on our two SDRAM chips preventing 16 bit and 8 bit access from working properly. Only 32 bit access was fine.

Problem now solved!

Ah, that's good to hear! 🙂

/Martin