any idea about SDMMC CRC error with HAL_MMC_ReadBlocks function?

[j.kouadio]

I am currently programming an eMMC(SDMMC) card with an STM32U575 microcontroller.

In 4 bit mode it works perfectly, but in 8 bit mode, I have a CRC error (HAL_MMC_ERROR_DATA_CRC_FAIL) in the HAL_MMC_ReadBlocks function called by fx_media_open.

NB: I call fx_media_format before fx_media_open.

When I compare the data I get in 4 bits and 8 bits mode, the first byte is not the same.

Any idea about that error?

Thanks in advance.

[Tesla DeLorean]

Unfortunately don't have any U5 boards, and ones I can find don't look to support 8-bit eMMC

Looks like a timing/synchronization issue possibly.

Does it work if you half the speed?

I did get 8-bit eMMC working quite well on the H745-DISCO/H750-DK boards. Needed to use DMA to service burst transfer rates.

[j.kouadio]

Hi @Community member​ 

I tried it, it doesn't change anything. It is the same error.

[j.kouadio]

Hi @Community member​ 

Which eMMC did you use, have you found the evaluation board on internet. Could you please send me the link?

[Tesla DeLorean]

Between myself, and those I've worked with, Toshiba, Samsung, SanDisk, Kingston, Greenliant in various sizes up to 128GB. Predominantly used ODROID modules (based on cost/availability), clamshell fixturing, and custom boards (where 8-bit and signal integrity was important).

The behaviour of 256 and 512 GB device should be similar, they just weren't cost effective, certainly in board-bringup / validation context, but FatFs has been tested out to 400 GB, but that's getting to the outer fringe of what makes sense on a MCU.

[j.kouadio]

And with greenliant EVB, people you worked with never met CRC failed problem in 8 bit mode for HAL_MMC_ReadBlocks. That's surprising.

[Piranha]

> the first byte is not the same

It's not just different - the first byte is missing and the whole block in the second screenshot is shifted by one byte.

[j.kouadio]

Yes, I'm trying to understand what's wrong. Write function works in 8 bit mode but read function does not