SPI with SD card module in Arduino - Mini Project: Build & Apply

SPI with SD card module

📖 Scenario: You want to save some text data to an SD card using an Arduino and an SD card module connected via SPI. This is useful for logging sensor data or storing information without a computer.

🎯 Goal: Build a simple Arduino program that initializes the SD card using SPI, creates a file, writes a line of text to it, and then closes the file.

📋 What You'll Learn

Use the SPI library to communicate with the SD card module

Use the SD library to handle the SD card

Initialize the SD card on chip select pin 10

Create a file named log.txt on the SD card

Write the text Hello, SD card! to the file

Close the file after writing

Print SD card initialized. if initialization succeeds

Print Initialization failed! if initialization fails

💡 Why This Matters

🌍 Real World

Logging sensor data or events to an SD card for later analysis without needing a computer connected.

💼 Career

Many embedded systems and IoT devices use SD cards for data storage. Knowing how to use SPI and SD libraries is essential for hardware programming jobs.

1

Setup SPI and SD card libraries

Include the SPI.h and SD.h libraries at the top of your sketch. Then create a constant integer called chipSelect and set it to 10.

Arduino

# Include SPI and SD libraries
// Your code here

Hint

Use #include <SPI.h> and #include <SD.h> to include the libraries. Then write const int chipSelect = 10;.

2

Initialize the SD card in setup()

Write the setup() function. Inside it, start serial communication at 9600 baud with Serial.begin(9600). Then initialize the SD card with SD.begin(chipSelect). If initialization succeeds, print SD card initialized. to serial. Otherwise, print Initialization failed!.

Arduino

#include 
#include 

const int chipSelect = 10;

void setup() {
  // Your code here
}

void loop() {
  // leave empty
}

Hint

Use Serial.begin(9600); to start serial. Then check if (SD.begin(chipSelect)) to test SD card. Use Serial.println() to print messages.

3

Create and write to a file on the SD card

Inside the setup() function, after SD card initialization, create a File object named myFile by opening log.txt in write mode using SD.open("log.txt", FILE_WRITE). Then write the text Hello, SD card! to myFile. Finally, close myFile.

Arduino

#include 
#include 

const int chipSelect = 10;

void setup() {
  Serial.begin(9600);
  if (SD.begin(chipSelect)) {
    Serial.println("SD card initialized.");
    // Your code here
  } else {
    Serial.println("Initialization failed!");
  }
}

void loop() {
  // leave empty
}

Hint

Use File myFile = SD.open("log.txt", FILE_WRITE); to open the file. Then write with myFile.println("Hello, SD card!"); and close with myFile.close();.

4

Print confirmation after writing to the file

After closing the file, print Data written to log.txt to the serial monitor inside the setup() function.

Arduino

#include 
#include 

const int chipSelect = 10;

void setup() {
  Serial.begin(9600);
  if (SD.begin(chipSelect)) {
    Serial.println("SD card initialized.");
    File myFile = SD.open("log.txt", FILE_WRITE);
    if (myFile) {
      myFile.println("Hello, SD card!");
      myFile.close();
      // Your code here
    }
  } else {
    Serial.println("Initialization failed!");
  }
}

void loop() {
  // leave empty
}

Hint

Use Serial.println("Data written to log.txt"); after closing the file.