I'm using an STM32H750B-DK for my project with 800x480 LCD using ext. SDRAM for framebuffer. I was only able to get the STM32H750VTB6 device for final production. When I build that device I get framebuffer to big. How do add an ext. SDRAM to the VTB6?

[radioman]

In the cubeMX FMC configuration I don't see SDRAM listed.

[TDK]

The STM32H750VBT6 is an LQFP100 package. The LQFP100 package doesn't have the necessary pins broken out to support SDRAM. For example, FMC_A0 is missing.

Therefore, you can't use SDRAM on that chip which is why CubeMX doesn't list it as an option.

[radioman]

Thank you. I was afraid of that. This chip shortage is killing me.

I'll have to try the F series if I can get any.

[radioman]

Can external FLASH be used as a framebuffer? the VBT6 does support that.

[TDK]

Flash is slow, probably not. But there are other RAM options via the FMC that you can use.

[radioman]

Thanks. I'll look into that.

[radioman]

I have moved my project to the Nucleo-H7A3ZI-Q dev. board and have added the APS1604M-3SQR PSRAM chip to use as a framebuffer. I have followed the instructions in AN5050 for the OCTOSPI settings using QUADSPI. I did not see any mention of configuring the FMC so that is disabled. I added the test functions listed in AN5050 to write and read to RAM. I first run EnterQuadMode() then EnableMemMappedQuadMode() and then the test loop but it is not storing the values. If I examine the memory location 0x90000000 when the program is paused it shows all 8s and I can't manually write a value to it. I have the clock to the OCTOSPI set to 200 MHz and the clock prescaller value in the OCTOSPI parameter settings set to 3. I also added the line "PSRAM  (xrw) : ORIGIN = 0x90000000, LENGTH = 2M" to the linked script. The RAM chip is soldered to a small PCB with 3" leads to the dev board and a bypass cap at the chip. Is there anything else I should be checking?

[radioman]

I did a reset to the clock configuration and set the clock for the the OCTOSPI back to 200 MHz and now I can write manually but the test program now is showing random values.