#include <SPI.h>
#include <SD.h>
 
#ifndef SD_CS_PIN
#define SD_CS_PIN 10    // D10
#endif
 
void listDir(File dir, int depth = 0) {
  while (true) {
    File entry = dir.openNextFile();
    if (!entry) break;
 
    for (int i = 0; i < depth; i++) Serial.print("  ");
 
    Serial.print(entry.name());
    if (entry.isDirectory()) {
      Serial.println("/");
      listDir(entry, depth + 1);
    } else {
      Serial.print("  ");
      Serial.print(entry.size());
      Serial.println(" bytes");
    }
    entry.close();
  }
}
 
void setup() {
  Serial.begin(115200);
  Serial.println("Initializing SD card...");
 
  pinMode(SD_CS_PIN, OUTPUT);
  digitalWrite(SD_CS_PIN, HIGH);  // keep CS high
 
  SPI.begin();     // Start SPI
 
  if (!SD.begin(SD_CS_PIN)) {
    Serial.println("SD init failed. Check wiring, CS pin, and FAT32 format.");
    while (1);
  }
 
  Serial.println("SD init OK. Listing root directory:");
 
  File root = SD.open("/");
  listDir(root);
  root.close();
}
 
void loop() {}