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STM32H745 SDMMC block reads returning empty

Associate II


I am working on trying to get the SDMMC1 on the stm32h745 to function properly. Currently I have this for my current initialization of the SDMMC and it does not return any errors. 

hsd1.Instance = SDMMC1;
hsd1.Init.ClockEdge = SDMMC_CLOCK_EDGE_RISING;
hsd1.Init.BusWide = SDMMC_BUS_WIDE_1B; 
hsd1.Init.ClockDiv = 0;

if (HAL_SD_Init(&hsd1) != HAL_OK) {
if (HAL_SD_ConfigWideBusOperation(&hsd1, SDMMC_BUS_WIDE_4B) != HAL_OK) {


After this is done, I try to use the HAL_SD_ReadBlocks_IT(); and also this does not return any errors. The issue I am having is the return data buffer has no data in it when this function finishes. Currently I am not sure what the issue might be, the clocks and appear as they are sending data but I am getting nothing in my return data. Any thoughts or ideas on what might resolve this problem? 


Chief II


so you want use sdcard - right ?

And no file system , no fatfs , no mount  ?

Anyway - at first stay on 1 bit mode . (After working fine, can try 4 bit ..more critical)

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Yes I am using a sd card and will eventually implement fatfs, but was trying to get the SDMMC to work first. I am currently having no luck in getting the system to get any data running in 1 bit mode. 

Ok, i can only tell, how i did (always):

install/set in Cube fatfs , sdcard ...etc. (no dma );

then first use a working sdcard , try mount . If this win the price . 🙂

fresult = f_mount(&SDfs, (TCHAR const*)SDPath, 1);	// SD card mount, 1 = now !

fresult = 0 =  no error . (As long this is not working, you have a hardware problem.)

First important thing: hardware ->

(in Cube) sd-pins setting : set on all pins : pullup , speed medium ; clk (i use ) 100MHz , div 1 (-> 50MHz for card).

And short lines to card , cpu -- card : max. 50mm (otherwise...good luck. )

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ST Employee

Hello @Matt__ 


Please refer to the example STM32H743I-EVAL/Examples/SD/SD_ReadWrite_IT  to check what is missing in your application. 

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ST Employee

Hello @Matt__ 

1.for your code, since you configure BisWide to 1B by  "hsd1.Init.BusWide = SDMMC_BUS_WIDE_1B; ", why you configure BisWide to 4B later by "if (HAL_SD_ConfigWideBusOperation(&hsd1, SDMMC_BUS_WIDE_4B) != HAL_OK)"?

below is my code:

/* uSD device interface configuration */
hsd->Instance = SDMMC1;
hsd->Init.ClockEdge = SDMMC_CLOCK_EDGE_RISING;
hsd->Init.BusWide = SDMMC_BUS_WIDE_4B;
// (SD ker CLK: 200M) SDMMC_HSpeed_CLK_DIV(2) or SDMMC_NSpeed_CLK_DIV(4)
hsd->Init.ClockDiv = 4;
// 1V8 Transceiver/Switcher not present
hsd->Init.TranceiverPresent = SDMMC_TRANSCEIVER_NOT_PRESENT;

/* HAL SD initialization */
if(HAL_SD_Init(hsd) != HAL_OK)
     ret = HAL_ERROR;

if(HAL_SD_ConfigWideBusOperation(&hsd_sdmmc[Instance], SDMMC_BUS_WIDE_4B) != HAL_OK)

(void)HAL_SD_ConfigSpeedBusOperation(&hsd_sdmmc[Instance], SDMMC_SPEED_MODE_HIGH);

2. I have met similar problem before, the root cause is that the SD card have several kinds, high-speed and low-speed, when I insert the low-speed SD card, it didn't work, but when I insert high-speed card, it worked, so can you check if your problem is same as mine?

So I was able to get the f_mount to succeed but only at low speeds. Currently I cannot figure out how to get past 6Mhz at 4 bits bandwidth and have the f_mount succeed. I have tried adjusting the clocks in the cubemx but can't seem to get any faster. Any ideas of what might be limiting this? 

Good ! First success ... 🙂

Any ideas of what might be limiting this? 

Hardware !

Still no statement : And short lines to card , cpu -- card : max. 50mm (otherwise...good luck. )

How long is distance cpu -- card ?

The cpu/sdmmc can work at 50M /4bit with sdcard - i have it here, running every day .

And only (!) use 1bit mode , until this working up to 50M without any problem.

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So the lines are only 45mm long, they are not shorted. There is a series resistor on all lines to help clean up the signal and pull up resistors to 3.3v on all lines except clk. I have an oscilloscope on the lines and the signals look clean coming across to the card



so value of pullups, series r ?

And cpu port/speed setting ?

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