Memory for DPI Frame buffer... Quad SPI NOR Flash and/or SDRAM

[Ricko]

Hi,

I have been reading a few app notes but still a bit confused about some things...

A custom board I am working with has an STM32U5G9VJT6Q MCU driving a DSI touch display. The PCB has QSPI and SDMMC but it does not have SDRAM.

In the application, the graphics to be displayed are only simple graphics and very slow graphic animation (think 2 frames GIF), no photos and no videos.

A few clarifications if someone could please explain:

1. What implications and/or restrictions are present because of the lack of SDRAM?

2. Can the SDMMC or the QSPI act as the frame buffer given there is no SDRAM on the PCB)?

3. if yes, which one would be preferred the preferred choice?

4. Considering that it is only simple graphics/slow-graphic-animation, can the images be fetched directly from the SDMMC or the QSPI through the DMA?

 

Thank you :)

[Tesla DeLorean]

Well the memory needs to be within the addressable space.

Even with static images the display typically paints at 50 or 60 Hz. Check the pixel clock expectations of the display.

QSPI can at least be mapped into memory. You'd have to check if the bandwidth is adequate. 

SDMMC can hold data but it can't be piped via LTDC/DSI

[MM..1]

Maybe start read docu and after maybe ask . U5 is designed for save external components,

Result is normal application dont require fetch from QSPI or SD, but can store GUI when is bigger as flash.
STM demo store in QSPI for example long animation. (30M used from 64)

Frambuffer placing priority is
   1. top internal DMA usable SRAM

   2. if SRAM is low SDRAM 32bit

   3. SDRAM 16bit

   4. OSPIRAM (8 bit)

and for displays with own buffers exist between 1 and 2 mode with partial buffer in internal.