How to interface micro SD cards with STM32

Learn how to interface micro SD cards with STM32 microcontrollers using the SPI protocol. This article provides a step-by-step guide and example code to demonstrate how to use micro SD cards in STM32 microcontrollers, specifically using the STM32CubeIDE and STM32F4 Discovery board.

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Micro SD cards:

Micro SD cards are widely used in embedded systems to store data such as images, videos, and other files. STM32 microcontrollers from STMicroelectronics are popular choices for embedded systems due to their powerful processing capabilities and rich peripheral set. In this article, we will discuss the basics of micro SD cards interfacing with STM32 microcontrollers and provide an example code to demonstrate how to use micro SD cards in STM32 microcontrollers.

Basics of how to interface micro SD cards with STM32:

Micro SD cards are small, portable storage devices that use a serial communication protocol to transfer data. The micro SD card interface is based on the Serial Peripheral Interface (SPI) protocol, which is a synchronous communication protocol used to communicate between microcontrollers and peripheral devices.

To use micro SD cards in STM32 microcontrollers, the first step is to select the appropriate STM32 microcontroller that supports SPI communication. STMicroelectronics offers a wide range of STM32 microcontrollers with SPI support, including STM32F4, STM32F7, STM32L4, and STM32H7 series.

The second step is to configure the SPI peripheral of the STM32 microcontroller. The SPI peripheral in STM32 microcontrollers is typically divided into three main blocks: the SPI interface, the SPI data buffer, and the SPI control and status registers.

Example Code for Micro SD Card Interfacing with STM32:

To demonstrate how to use micro SD cards with STM32 microcontrollers, we will use the STM32CubeIDE integrated development environment (IDE) and STM32F4 Discovery board. The STM32CubeIDE is a free, cross-platform IDE that provides a comprehensive development environment for STM32 microcontrollers.

In this example, we will use the SPI interface of the STM32 microcontroller to communicate with the micro SD card. We will write a simple program that reads a text file from the micro SD card and displays it on the console.

Step 1: Create a new project in STM32CubeIDE

Open STM32CubeIDE and create a new project using the STM32F4 Discovery board. Select “SPI” as the middleware and “SDIO/SDMMC” as the communication protocol. The SDIO/SDMMC protocol allows us to interface with the micro SD card using the SPI interface of the STM32 microcontroller.

Step 2: Configure the SPI peripheral

In the STM32CubeMX configuration tool, enable the SPI peripheral and configure the clock speed, data size, and other parameters as per the micro SD card’s specifications. Configure the chip select pin as per the board’s schematic.

Step 3: Write code:

Here is an example code for micro SD cards interfacing with STM32 microcontrollers using the SPI protocol. This code is written in C language and uses the STM32CubeIDE and STM32F4 Discovery board.

#include "main.h"
#include "stm32f4xx_hal.h"
#include "fatfs.h"

/* Private variables */
SPI_HandleTypeDef hspi1;
FATFS FatFs;
FIL Fil;
FRESULT fresult;
char buffer[1024];

/* Private function prototypes */
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_SPI1_Init(void);

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_SPI1_Init();

  f_mount(&FatFs, "", 0);

  fresult = f_open(&Fil, "test.txt", FA_READ);
  if (fresult == FR_OK)
  {
    while (f_gets(buffer, sizeof(buffer), &Fil))
    {
      printf("%s", buffer);
    }
    f_close(&Fil);
  }
  else
  {
    printf("Error opening file!\n");
  }

  while (1)
  {
    /* Infinite loop */
  }
}
...

In this project, the STM32F4 Discovery board is used, you can use similar boards or MCU.

Hope this will help you. See you soon with the next article. Thanks.

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