Micro-SD Card Reader 3.3V

#include <SPI.h>
#include <SD.h>

const int SD_CS_PIN = 10;

void setup() {
  Serial.begin(9600);
  while (!Serial) {
    ;
  }

  Serial.println("Micro-SD Card Reader 3.3V example");
  Serial.println("Initializing SD card...");

  pinMode(SD_CS_PIN, OUTPUT);
  digitalWrite(SD_CS_PIN, HIGH);

  if (!SD.begin(SD_CS_PIN)) {
    Serial.println("SD card initialization failed!");
    Serial.println("Check wiring, card format, and that the module is powered correctly.");
    while (true) {
      delay(1000);
    }
  }

  Serial.println("SD card initialized successfully.");

  File root = SD.open("/");
  if (root) {
    Serial.println("Files on the card:");
    printDirectory(root, 0);
    root.close();
  } else {
    Serial.println("Could not open root directory.");
  }
}

void loop() {
  // Simple periodic status message so you can see the sketch is running.
  Serial.println("SD card ready.");
  delay(2000);
}

void printDirectory(File dir, int numTabs) {
  while (true) {
    File entry = dir.openNextFile();
    if (!entry) {
      break;
    }

    for (int i = 0; i < numTabs; i++) {
      Serial.print('\t');
    }

    Serial.print(entry.name());
    if (entry.isDirectory()) {
      Serial.println("/");
      printDirectory(entry, numTabs + 1);
    } else {
      Serial.print("\t");
      Serial.println(entry.size(), DEC);
    }

    entry.close();
  }
}