Is it possible to use FatFs with SD Card as extended SDRAM?

[Costas Papachristou]

Hi,

I was wondering if it's possible to use FatFs with SD Card as extended SRAM, or maybe by setting the FMC to map to the FatFs or SD Card in some way. I have a project that uses an RGB Display of 480x272 (RGB565 mode), so the RAM space needed is 130560 bytes (uint16_t), but the STM32F429VIT6 I'm using has only 256KB. So, I want to store the array variable of the LTDC controller in this extended space (pLayerCfg.FBStartAdress = (uint32_t)&image_intro1;)

If it's not possible, I have to make another PCB and interface an SDRAM IC to the uC. So, it would save me time and money if I can get it to work. I'm not sure though that the FatFs will be fast enough for the task. I just want to display some menus (static images that is).

Any help would be greatly appreciated!

Thanks

Kostas

[TDK]

You can't use the FMC to map to an SD card, nor can you use an SD card the same way as you can use SRAM. There are fundamental differences here, primarily the massive access time and the inability to address individual bytes.

[Costas Papachristou]

Ok, so the only way is to add extended SDRAM. The problem is that due to the current situation all STM32F429/439/469 (LQFP-208) uControllers are out of stock until the end of 2022 :(

Anyway, thanks a lot for the reply!