Need help getting SD+FATFS working with an STM32H747I-Disco

[tgrant]

I'm trying to use the SD card reader on the STM32H747I-Disco with FatFs. It's working as expected with the M7 core -- I'm able to initialize the SD interface and the filesystem, and access files on the SD card.

However, when I perform the same initialization using the M4 core (which is the core I would like to access the SD card), I get FR_DISK_ERROR when I try to open files or directories.

I'm using the BSP initialization functions. The SD interface initializes correctly (without error, anyway), and BSP_SD_GetCardInfo returns the correct information. After I link the driver, I'm able to mount the SD card, but attempting to open a file fails.

The failing part of my setup code looks something like this:

 if( FATFS_LinkDriver( &SD_Driver, sdPath ) != 0 )
 {
 sendString( "FATFS error: unable to link driver!\r\n" );
 }
 else if( (res = f_mount( &sdFatFs, (TCHAR const*)sdPath, 0 )) != FR_OK )
 {
 sendString( "FATFS error: unable to mount SD card!\r\n" );
 }
 else if( (res = f_open( &file, "test.txt", FA_READ )) != FR_OK )
 {
 // This call fails with FR_DISK_ERROR
 sendString( "FATFS error: unable to open file!\r\n" );
 }

Does anybody know why FatFs would work on one core and not the other? Is anyone successfully using the SD interface with the M4 core?

[tgrant]

I have found a solution.

The M7 is being clocked at 400MHz, and the M4 is at 200MHz. I noticed that doubling the clock divider set in BSP_SD_Init caused the file operations to start working on the M4. I wasn't too keen on modifying that function, so instead I found the clock source for SDMMC1 (PLL1) and set the divider to supply a 200MHz clock to the SDMMC.

It's not clear to me what the relationship between the different clocks is, but I'm happy to have it working for now.

[TurtleBeach]

@tgrant,

Would you be willing to share a few more details/guidance related to how you managed to get an SD Card / FatFS working on the DISCO board?

I have been struggling for the past 3 days, to no avail. I am using CubeIDE 1.1, with CubeMX 5.4. Since there is no direct H747-DISCO SD Card project/example, I have been attempting to modify the H747-EVAL example for FatFS. I actually want to access the SD Card from the M7 processor, but the SD Card is not getting initialized. I have tried to faithfully follow the rat's nest of #defines and #includes to get the proper BSP_SD_Init code, but I don't think I have it, and I also think the problem is related to clock speeds. In my case, I **think** the right clocks are being initialized in the SystemClock_Config() that I pulled from the -EVAL application, but I am frankly not sure (I expect to eventually figure out what I need to know about the clocks and configuration, but right now I just need working code that will let me pull a couple of files off an SD Card). I did not expect this to be the nightmare it has become.

Thanks.

[Tesla DeLorean]

>>Since there is no direct H747-DISCO SD Card project/example...

STM32Cube_FW_H7_V1.5.0\Projects\STM32H747I-DISCO\Examples\JPEG\JPEG_DecodingUsingFs_DMA

[LBarn.1]

This seems very similar to the issue I posted in December. Would the stack and heap size have any affect on this? Where are they stored in the Cube IDE project?

Thanks in advance for your reply.

[Tesla DeLorean]

For CubeIDE (GNU/GCC) the stack/heap generally commingled, and are called out in the linker script. The actually allocator code is actually in the __sbrk() code in newlibs.c or syscalls.c

Generally you want the stack in the fastest available memory (DTCM SRAM)

The H7 has some particularly difficult memory/dma controller issues, so one must pay attention to memory alignment, and cache coherency.