How to Implement FatFs for Logging Sensor Data to SD Card with STM32F4

Introduction

In this tutorial, we will implement FatFs, a generic FAT file system module for small embedded systems, to log sensor data to an SD card using the STM32F4 microcontroller. We will configure the system to sample data at a frequency of 1Hz. This guide covers prerequisites, necessary parts and tools, step-by-step implementation, troubleshooting tips, and a brief conclusion.

Prerequisites

• Basic understanding of embedded systems and STM32 programming
• STM32F4 development board
• SD card with adapter
• Keil uVision or STM32CubeIDE installed
• HAL library for STM32F4
• FatFs library files
• Sensor module (e.g., temperature or humidity sensor)

Parts/Tools

• STM32F4 development board
• SD card (e.g., 16GB) and adapter
• Connecting wires
• PC with IDE for development

Steps

1. Set up the development environment
   • Install STM32CubeIDE or Keil uVision.
   • Create a new STM32 project targeting the STM32F4 series.
2. Configure GPIO for SD card interface
   • Set up SPI communication for the SD card:

   
       // Example for STM32CubeMX
       // Enable SPI1, set mode to Master, and configure GPIO pins
       

   • Configure the CS (Chip Select) pin for the SD card:

   
       // Example: GPIO pin configuration
       HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_SET); // Set CS high
       

3. Integrate FatFs into the project
   • Download FatFs from its official website.
   • Add the FatFs source files to your project:

   
       // Add ff.c, ff.h, and other necessary files to your project
       

4. Initialize the SD card and FatFs
   • In your main.c file, include the necessary headers:

   
       #include "ff.h" // FatFs header
       #include "diskio.h" // Disk I/O header
       

   • Initialize the SD card and mount the file system:

   
       FATFS fs;
       if (f_mount(&fs, "", 1) != FR_OK) {
           // Handle error
       }
       

5. Create a file for logging
   • Define a function to create and open a log file:

   
       void createLogFile() {
           FIL fil;
           if (f_open(&fil, "log.txt", FA_WRITE | FA_CREATE_ALWAYS) == FR_OK) {
               // File is created successfully
               f_close(&fil);
           }
       }
       

6. Read sensor data and log it
   • Implement a function to read sensor data:

   
       float readSensorData() {
           // Code to read from the sensor
           return sensorValue; // Replace with actual sensor reading
       }
       

   • Log data at 1Hz:

   
       while (1) {
           float data = readSensorData();
           logData(data);
           HAL_Delay(1000); // 1 second delay
       }
       

7. Implement the logData function
   • Write the sensor data to the log file:

   
       void logData(float data) {
           FIL fil;
           char log[50];
           if (f_open(&fil, "log.txt", FA_WRITE | FA_OPEN_APPEND) == FR_OK) {
               sprintf(log, "Data: %.2fn", data);
               f_write(&fil, log, strlen(log), NULL);
               f_close(&fil);
           }
       }
       

Troubleshooting

• SD card not recognized: Ensure the SD card is properly connected and formatted to FAT32.
• File not created: Check for proper permissions and ensure the FatFs library is correctly integrated.
• Data not logged: Verify that the sensor is functioning and check for any errors during file write operations.

Conclusion

In this tutorial, we have successfully implemented FatFs to log sensor data to an SD card using the STM32F4 microcontroller at a sampling rate of 1Hz. You can expand on this project by adding features like data visualization or real-time processing based on your application needs. Happy coding!