#include <SdFat.h>                // SD card & FAT filesystem library

#define SD_CS   4 // SD card select pin

SdFat SD;         // SD card filesystem

void setup(void) {

  Serial.begin(9600);
  Serial.print(F("Initializing filesystem..."));

  if (!SD.begin(SD_CS, SD_SCK_MHZ(25))) { // ESP32 requires 25 MHz limit
    Serial.println(F("SD begin() failed"));
    for (;;); // Fatal error, do not continue
  }
  Serial.println(F("OK!"));
}
  void loop() {
  }