STM32F479 datasheet(88/91 Pages) STMICROELECTRONICS

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Frequently asked questions

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Frequently asked questions

This section summarizes the most frequently asked questions regarding the LTDC usage

and configurations.

Table 18. Frequently asked questions

Question

Answer

Which is the LTDC maximum

supported resolution?

There is no absolute maximum resolution since it depends

on several parameters such as:

– the color depth

– the used SDRAM bus width

– system operating speed (HCLK)

– number of AHB masters accessing concurrently to

memory used for framebuffer.

See Section 4.2.2: Checking display compatibility

considering the memory bandwidth requirements.

Does the STM32F4 Series or the

STM32F7 Series support a 1280 x

720p 60 Hz resolution?

Yes, see examples in Section 4.2.2: Checking display

compatibility considering the memory bandwidth

requirements.

Which SDRAM bus width should be

used for a specific resolution?

There is not an exact specific bus width, it depends on the

resolution, the color depth and whether the SDRAM is

shared with other AHB masters or not.

The higher SDRAM bus width, the better. An SDRAM 32-bit

provides the best possible performances.

How to get the maximal supported

resolution for a specific hardware?

Refer to Section 4.2.2: Checking display compatibility

considering the memory bandwidth requirements.

Does LTDC support OLED displays?

Yes, if the OLED display has a parallel RGB interface.

Does LTDC support STN displays?

No, STN displays are not supported by LTDC.

Why the image is displayed with red

and blue colors swapped?

This is because the image is not stored into memory

respecting the configured pixel input format (see

Section 4.8.1: Converting images to C files).

Does LTDC support gray scale?

Yes, it is possible by using the L8 mode and using a correct

CLUT (R=G=B).

Why the display is bad (displaying

bad visual effects)?

Many factors can lead to a bad visual effect, the user can

perform the following checks:

– Check if the used display is correctly initialized / configured

(some displays need an initialization / configuration

sequence)

– Check if the LTDC timings and layer parameters are

correctly set (see example in Section 6.2.4)

– Display an image directly from the internal Flash (see

example in Section 6.2.5)

– Check if there is a non-synchronization between the LTDC

and the framebuffer update (by DMA2D or CPU), see

Section 4.4.2.

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