RGB controller interface and memory

Pkats.1 · ‎2021-01-25

hey,

as i saw at the EVB, the driver uses the SDRAM as a memory source for the RGB interface.

the SDRAM size is 256Mbit while the SRAM is 16Mbit.

in my application, my plan is to use the SRAM only.

Do you see any problem to use the SRAM memory for the RGB controller?

Does anyone tried to upload a pic or even access to a certain pixel by using the SRAM ?

Moreover, when i showing a static pic on the screen, does the controller sends the pixels Periodically (50HZ) or only one time ?

Thank you!

waclawek.jan · ‎2021-01-26

What EVB? What SRAM?

>Do you see any problem to use the SRAM memory for the RGB controller?

No, if framebuffer(s) fits into the given memory, and if you don't mind that accessing that SRAM from processor or other bushmaster may collide with the LCD controller (and DMA2D if used).

> does the controller sends the pixels Periodically (50HZ)

Yes, if it is a controller-less display.

JW

Pkats.1 · ‎2021-01-26

stm32h753-EVAL , SRAM CY7C1061GE30-10BV1XIT.

when i defined the memory source from SDRAM to SRAM, i saw "spreading" of the pixels, maybe i should Make adjustments in the Driver?

About the Periodically pixels , the DMA moving frame of pixels to a dedicated buffer of the RGB Controller ? could you explain more about the chain starting from memory (SRAM for example until the Screen) ?

Thanks

waclawek.jan · ‎2021-01-26

> maybe i should Make adjustments in the Driver?

Sorry I am not interested in debugging FMC code, especially if it's some "library" like Cube.

> DMA moving frame of pixels to a dedicated buffer of the RGB Controller ?

That depends on your software.

If you use a controller-less LCD, the LTDC periodically refreshes the picture on it, i.e. within the say 50Hz refresh rate it has to pick every pixel from the framebuffer in memory and output it on its pins for the LCD. This happens regardless of what your software does, even if the picture is static and the framebuffer in RAM does not change.

If your software wants some changing pictures, then it has to write somehow to the framebuffer; one of the ways is to use the DMA2D with its facilities.

JW