Reading data from SD card in Arduino - Mini Project: Build & Apply

Reading data from SD card

📖 Scenario: You have a small Arduino project that needs to read text data stored on an SD card. This is common in projects like data loggers or music players where the Arduino reads files from the SD card.

🎯 Goal: Build a simple Arduino program that reads the contents of a text file called data.txt from an SD card and prints it to the Serial Monitor.

📋 What You'll Learn

Use the SD library to access the SD card

Initialize the SD card on pin 10

Open the file data.txt for reading

Read the file content line by line

Print each line to the Serial Monitor

💡 Why This Matters

🌍 Real World

Reading data from an SD card is useful in projects like data loggers, audio players, or any device that needs to access stored files.

💼 Career

Understanding how to interface with SD cards is important for embedded systems developers and IoT engineers working with external storage.

1

Set up SD card and Serial communication

Write code to include the SD and SPI libraries, create a File variable called myFile, and start Serial communication at 9600 baud inside setup(). Also, initialize the SD card on pin 10 using SD.begin(10) and print "SD card initialized." if successful.

Arduino

# Include SD and SPI libraries
#include 
#include 

File myFile;

void setup() {
  Serial.begin(9600);
  // Initialize SD card on pin 10
  // Your code here
}

void loop() {
  // Empty loop
}

Need a hint?

Remember to include both SD.h and SPI.h libraries. Use SD.begin(10) to start the SD card on pin 10.

2

Open the file for reading

Inside setup(), after initializing the SD card, open the file data.txt for reading using myFile = SD.open("data.txt"). Then check if myFile is valid (opened successfully) and print "File opened successfully." if it is.

Arduino

#include 
#include 

File myFile;

void setup() {
  Serial.begin(9600);
  if (SD.begin(10)) {
    Serial.println("SD card initialized.");
  } else {
    Serial.println("SD card initialization failed.");
  }
  
  // Open the file data.txt for reading
  // Your code here
}

void loop() {
  // Empty loop
}

Need a hint?

Use SD.open("data.txt") to open the file. Check if myFile is true to confirm it opened.

3

Read the file content line by line

Inside setup(), after opening the file, use a while loop with myFile.available() to read each character from the file. Use myFile.read() to get each character and print it to Serial using Serial.write().

Arduino

#include 
#include 

File myFile;

void setup() {
  Serial.begin(9600);
  if (SD.begin(10)) {
    Serial.println("SD card initialized.");
  } else {
    Serial.println("SD card initialization failed.");
  }

  myFile = SD.open("data.txt");
  if (myFile) {
    Serial.println("File opened successfully.");
    // Read and print file content
    // Your code here
  } else {
    Serial.println("Failed to open file.");
  }
}

void loop() {
  // Empty loop
}

Need a hint?

Use while (myFile.available()) to loop through the file. Read each character with myFile.read() and print it with Serial.write(). Don't forget to close the file.

4

Print the file content to Serial Monitor

Add a Serial.println("End of file."); statement after closing the file to indicate the file reading is complete.

Arduino

#include 
#include 

File myFile;

void setup() {
  Serial.begin(9600);
  if (SD.begin(10)) {
    Serial.println("SD card initialized.");
  } else {
    Serial.println("SD card initialization failed.");
  }

  myFile = SD.open("data.txt");
  if (myFile) {
    Serial.println("File opened successfully.");
    while (myFile.available()) {
      char c = myFile.read();
      Serial.write(c);
    }
    myFile.close();
    // Your code here
  } else {
    Serial.println("Failed to open file.");
  }
}

void loop() {
  // Empty loop
}

Need a hint?

Print "End of file." after closing the file to show reading is done.