STM32Cube. Microcontroller STM32 and FatFs.

Hello to all!

Today we’ll try to connect SD-card to our STM32 microcontroller and to create a FAT filesystem on it. In order to test the filesystem we’ll create a new file and write some data to it.

.STM32 and FAT filesystem

In previous posts I’ve used the STM32F4-Discovery board, but today the development board with the STM32F10x MCU mounted on it will be tested. In spite of the fact that we’ll use another board, all the phases of creating the project will be the same 🙂 Let’s launch the STM32Cube and configure all needed units!

The SD-card is connected to the STM32 via SDIO interface, so, first of all, we should enable it. After that the SD-card checkbox will become available for checking:


As you see STM32Cube marks all pins involved in our project. Please note that UART4 and UART5 units became unavailable. It is connected with the fact that the pins needed for proper UART4/UART5 work are involved in SDIO interface connections.

Let’s proceed to the “Configuration” tab, where we can see the new modules available for some extra configuration:

STM32Cube configuration

If we click on the SDIO button, a new window, where the clock divider for SDIO interface can be set, will appear:

SDIO interface

Similarly, we can open a FatFs configuration window, but in this project we have no need of any extra settings of FAT. Thus, we can start a new project generation!

If we open the project in IDE we’ll see that besides initialization functions for all used units, STM32Cube calls one more function named FATFS_LinkDriver(). Let’s look into this function more carefully.

STM32Cube’ve generated the sd_diskio.c in order to implement write and read operations. It contains the following functions:


Moreover SD_Driver struct, which contains the pointers to these functions is defined. And the FATFS_LinkDriver() function is exactly what binds the SD_Driver struct and the current FAT disk number. As it is the first call of this function the disk number is set to 0. If we’ll decide to use one more disk, for example, NAND, we should pass number “1” into this function.

So, now it’s quite clear, let’s add some code in order to create a new file:

  FATFS fileSystem;
  FIL testFile;
  uint8_t testBuffer[16] = "SD write success";
  UINT testBytes;
  FRESULT res;
  if(f_mount(&fileSystem, SD_Path, 1) == FR_OK)
    uint8_t path[13] = "testfile.txt";
    path[12] = '\0';
    res = f_open(&testFile, (char*)path, FA_WRITE | FA_CREATE_ALWAYS);
    res = f_write(&testFile, testBuffer, 16, &testBytes);
    res = f_close(&testFile);
  /* Infinite loop */
  while (1)
  /* USER CODE END 3 */

This code creates a new file and writes an amount of data to it. After that the file is closed. If we’d forget to close the file the data wouldn’t be written. Now we can compile the project and program the MCU.

To check the result of our work we should take the SD-card out of the development board and insert it in the cardreader.

We can see the new file named testfile.txt with our data:

FatFs STM32

So the write operation was properly completed and our project is correct!

Well, I’ll stop here, thank you for your attention! 🙂

Full project can be found here – STM32Cube_SDCardProject

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17 thoughts on “STM32Cube. Microcontroller STM32 and FatFs.
  1. Thank you, I’m going to try this using Keil, I hope that it will work, but I have a question, there’s a problem if I’m using a uSd adapter for read and write?

    • As far as I know, STM32Cube doesn’t support SD-card and SPI interface, so all of the functions should be written by the user.

  2. Hi!
    Can you help me, how i should configure clock in STM32F4? Because in “SD 1 bit” mode everything is great but if i change to “SD 4 bit” mode it’s not working.

          • sorry for waiting, SD card is not working :/

            SD 1 bit working fine but SD 4 bit no :/ I don’t know why?
            What version of libraries did you use? Can you try do that for F4?
            I try this at STM32L4 and STM32F4, and the same problem :/
            1 bit working, 4 bit not :/

        • I have no boards with STM32F4 and SD-card =(
          I tried SDIO (4 bit) with STM32F10x with different versions of HAL and Cube and it always worked fine. Maybe there are some problems in electrical connection? Pull-up resistors? Does the card work properly without USB? Just writing/reading some blocks of data?

          • Electrical connection must be fine, because 1-bit mode works fine 🙂 I use F4Discovery with DM-STF4BB – so electrical must be ok 🙂
            So more i check it with standard module microsd with pull up resistor and the same problem :/

            Can i send you a code and maybe a film with everything?

  3. I am testing microsd with stm32f405rgt6. The weird thing is that the first run after power up fails when it opens the file to write. Then I reset the chip by manually pull NRST to ground. it works, open file, write and read file. I pull nrst again to ground. file reading/writing has no problem.
    The only problem is the first run.

    Therefore the hardware(like connection) should be fine. Software should be fine too. What is the problem in the first run?

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