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STM32F746, Pixel erros with VRAM in remapped SDRAM

Question asked by steinkamp.matthias on Oct 22, 2016
Hi there,

I have a F7 setup with running LTDC, DMA2D and SDRAM to drive a tft display. The VRAM buffer is defined in SDRAM memory.

When I use the standard SDRAM address mapping at 0xC0000000, the display works fine without pixel errors.

However, when I remap the SDRAM to 0x60000000 (__HAL_SYSCFG_REMAPMEMORY_FMC_SDRAM), the dispaly shows pixel errors. It's like the image/menu is loaded only up to 99%. Some pixels change to their final color after a short delay.

The reason because I remapped the SDRAM is because I placed the heap into SDRAM and need it to support unaligned access. That's only possible for addresses lower a certain value and 0xC0000000 is out of that range. I get HardFaults.

Can someone please confirm this pixel error problem with remapped SDRAM?
Is there a solution?

Thank you!

Best regards,
Matthias

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