Stm32l4r9 high pixel mipi dsi lcd

[er3481]

Hi,

I am trying to use touch gfx library on a stm32l4r9aii mcu and i use 454*454 pixel amoled lcd, i can not write anything to lcd, So i have noticed from webinar notes that L4R9 mcu can drive up to 450*450 mpi dsi displays. Is my problem about my mcu ? Or, if i will use external psram, can i drive 454*454 lcd with STM32L4R9?

Any advise

[StéphaneM]

Hello er3481

from the DSI standpoint , there is no limitation in the maximum supported resolution. In particular 800*480 resolution is reachable.

Refer to paragraph "30.4.3 Supported resolutions and frame rates" in RM0432 for more details.

The hint given in the webinar is an approximation depending on several parameters such as resolution but also display frame rate, DMA2D frequency.

Best regards,

Stéphane

[er3481]

Hi @St�phaneM​ 

If my problem is not about lcd resolution, what am i missing ? As i asked before, do i have to use external psram on my board ?

[MM..1]

Your MCU have 640k RAM then for framebuffer L8 you need 454x454 bytes, for RGB565 x2

or you can use partial framebuffer if display have own buffer usw...

[er3481]

Ok, i have settings below and FRAMEBUFFER start adress is shown as "20040000" ( i am using PSRAM and the bank address is 0x60000000).

How can i edit this address for 0x60000000?

[MM..1]

I recommend start display without all GFXMMU .... and apply it after it works.

Read Graphic memory optimization with STM32 Chrom-GRC™

[Tesla DeLorean]

Address probably in Linker Script (.LD), or related settings.

I suspect size and band-width constrained by Internal RAM, ie fast and 32-bit wide

[er3481]

Hi,

In fact i have long frame buffer and i want to address it to external psram. So i have added the psram line to .ld file:

MEMORY

{

 RAM     (xrw)  : ORIGIN = 0x20000000,  LENGTH = 256K

 FRAMEBUFFER (rw)   : ORIGIN = 0x60000000,  LENGTH = 384K

 FLASH    (rx)   : ORIGIN = 0x08000000,  LENGTH = 2048K

 OCTOSPI   (xrw)  : ORIGIN = 0x90000000,  LENGTH = 64M

 PSRAM  (rw)   : ORIGIN = 0x60000000,  LENGTH = 4M

}

But i am not sure there is something to do. I want to learn how to use external psram with framebuffer. Maybe you will give advises me.

Thanks

[MM..1]

duplicate origin ORIGIN = 0x60000000 dont help.

And in linker you need this only if plan using psram too for other purpose.