Micro SD Card Adapter Module 3.3V for ESP32 and ESP8266

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

const int SD_CS_PIN = 10;

void printFileToSerial(const char *filename) {
  File file = SD.open(filename, FILE_READ);
  if (!file) {
    Serial.print("Failed to open ");
    Serial.println(filename);
    return;
  }

  Serial.print("\nContents of ");
  Serial.println(filename);
  while (file.available()) {
    Serial.write(file.read());
  }
  Serial.println();
  file.close();
}

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

  Serial.println("Initializing Micro SD card...");

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

  Serial.println("SD card initialization done.");

  File root = SD.open("/");
  if (root) {
    Serial.println("Root directory:");
    while (true) {
      File entry = root.openNextFile();
      if (!entry) break;
      Serial.print("  ");
      Serial.print(entry.name());
      if (entry.isDirectory()) {
        Serial.println("/");
      } else {
        Serial.print("\t");
        Serial.println(entry.size());
      }
      entry.close();
    }
    root.close();
  }

  // Create a simple demo file if it does not already exist.
  if (!SD.exists("demo.txt")) {
    File file = SD.open("demo.txt", FILE_WRITE);
    if (file) {
      file.println("Hello from the Arduino Uno SD card example!");
      file.println("This file was created by the sketch.");
      file.close();
      Serial.println("Created demo.txt");
    } else {
      Serial.println("Could not create demo.txt");
    }
  }

  printFileToSerial("demo.txt");
  Serial.println("Setup complete.");
}

void loop() {
  // Periodically show that the card is still accessible.
  File file = SD.open("demo.txt", FILE_READ);
  if (file) {
    Serial.print("demo.txt size: ");
    Serial.println(file.size());
    file.close();
  } else {
    Serial.println("Could not reopen demo.txt");
  }

  delay(5000);
}