do I need an SDRAM?

[AGeis.4]

Hello,

I am in the process of making my own circuit board and using an f767 with 144 pins. I have integrated a QSPI and a 40-pin FPC for an 800x480px display. The LTDC is in RGB565. Unfortunately, I don't have any pins left for the SDRAM. So the question is, do I need the SDRAM? Can the QSPI replace it?

[MM..1]

If your f767 have ram for dynamic part on your screen , then you not require SDRAM.

Full dynamic in 565 = 2x800x480 bytes = 750kB plus heap and stack for your code.

Full dynamic in L8 is half of this.

And you can dont use full dynamic screen. Define window for example 640x400 for dynamic.

Background can fill full static screen from QSPI in LTDC second layer. Here you can use for example RGB888 ...

example

[AGeis.4]

So the 767 has a 512kb RAM which is already too small for the 800x460 display. And if I only use static applications, they can be stored on the QSPI. Does a gauge count as an animation?

[MM..1]

Try start with L8 framebuffer ARGB2222 fit your ram
too check if your LCD don’t have own memory ... partial framebuffer FMC mode ...

[LCE]

Be careful, the F7 does not support QSPI RAM in memory-mapped mode.

[AGeis.4]

What is the memory-mapped mode?

[MM..1]

You write about QSPI, but don’t define is FLASH or RAM. (I mean flash)
MM mode is read only direct access into FLASH type QSPI.

[AGeis.4]

I'd rather play it safe and include both an SDRAM and a QSPI by using the 208-pin option. SDRAM: AS4C4M16SB-6TIN.

[AGeis.4]

My display : https://www.adafruit.com/product/2354

[AGeis.4]

So, the F767 has an internal 512kb RAM. That means it's not enough for the large display. And the external RAM has 64 Mbit. Should that be enough? Do I need to split the SDRAM or would I need a second SDRAM for the animations?

[t.decker]

I also have a 800x480 LCD connected to a F767. I use 8MByte of external DRAM for the framebuffers. For performance reasons I put each of the 3 framebuffers in a separate RAM-bank (2MByte). But I think this would also work with the framebuffers aligned contiguous.

STM32F767BITX_FLASH.ld:

.sdram_bank0 0xC0000000 (NOLOAD) : /* MPU configured to Normal, Write through, no write allocate, shareable */
{
 *(.tgfx_framebuffer0)
 . = ALIGN(32);
 *(.sdram_bank0)
} >EXT_SDRAM
 
.sdram_bank1 0xC0200000(NOLOAD) : /* MPU configured to Normal, Write through, no write allocate, shareable */
{
 *(.tgfx_framebuffer1)
 . = ALIGN(32);
 *(.sdram_bank1)
} >EXT_SDRAM
 
.sdram_bank2 0xC0400000 (NOLOAD) : /* MPU configured to Normal, Write through, no write allocate, shareable */
{
 *(.tgfx_framebuffer2)
 . = ALIGN(32);
 *(.sdram_bank2)
} >EXT_SDRAM

TouchGFXHAL.cpp:

uint8_t framebuffer0[2][DISP_FRAMEBUF_HEIGHT][DISP_FRAMEBUF_WIDTH_PITCH] __attribute__((section(".tgfx_framebuffer0"))) __attribute__((aligned (1024)));
uint8_t framebuffer1[2][DISP_FRAMEBUF_HEIGHT][DISP_FRAMEBUF_WIDTH_PITCH] __attribute__((section(".tgfx_framebuffer1"))) __attribute__((aligned (1024)));
uint8_t framebuffer2[2][DISP_FRAMEBUF_HEIGHT][DISP_FRAMEBUF_WIDTH_PITCH] __attribute__((section(".tgfx_framebuffer2"))) __attribute__((aligned (1024)));
 
 
void TouchGFXHAL::initialize()
{
	[...]
	//TouchGFXGeneratedHAL::initialize();
	setFrameBufferStartAddresses((void*)framebuffer0, (void*)framebuffer1, (void*)framebuffer2);
	setFrameBufferSize(DISP_FRAMEBUF_WIDTH_PITCH, DISP_FRAMEBUF_HEIGHT);
	[...]
}