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STM32F429 LTDC 2Layer - Problem with external LCD (640x480)

Question asked by lohse.dirk on May 2, 2014
Latest reply on Oct 13, 2014 by dimopoulos.stavros
Hi, we use the STM32F429ZI with the STM32F4-Discovery-Board (with ILI9341-Display - landscape mode).

As example we use the "LTDC_Paint" - Example from the STM32CubeF4. Normally there is only the background-layer active. I can enable the second layer (foreground), paint something on it and set transparency - no problems.

Now we attached an external display from EDT (ETMV570G2DHU - 640x480px, portrait-mode, desoldered the ILI-Display) which works fine with the ONE Layer!!! from the example - also no problems.

But when i enable the foreground-layer and the background-layer at the same time - we got noise on the display. Switching between the two layers works and both are ok if they are not enabled at the same time.

I checked the Base-Adresses of the Framebuffers which are:
LAYER0 (background): 0xD000 0000 + 0x0013 0000
LAYER1(foreground): 0xD000 0000

So i have ~1.2 MBytes per framebuffer which should be enough for 640x480x4=0x0012 C000
I played around with these settigs - but i can't find an solution.

So my question: Why i cannot display 2 Layers at the same time an the display with an resolution of 640x480 pixels.