I have an Arduino Mega connected to an SD card reader (Catalex branded), that at least detects the card as it displays the info of the card. But when I try to create a file, it does not create it. I am using the following code:

if (SD.exists("data.txt")) {
  Serial.println("data.txt exists.");
} else {
  Serial.println("data.txt doesn't exist.");
File root=SD.open("data.txt", FILE_WRITE); //open of the File for writting
if (SD.exists("data.txt")) {
  Serial.println("data.txt exists.");
} else {
  Serial.println("data.txt doesn't exist.");

I also tried with this code:

File root2 = SD.open("file.txt", O_RDWR | O_APPEND);
    if (!root2) {
       // It failed, so try and make a new file.
        root2 = SD.open("file.txt", O_RDWR | O_CREAT);
        if (!root2) {
          // It failed too, so give up.
        Serial.println("Failed to open file.txt");


I also tried with this easier code and it does not work either:

#include <SD.h>

const int chipSelect = 10;
Sd2Card card;

void setup() {
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  Serial.print("Initializing SD card...");
  // see if the card is present and can be initialized:
  if (!SD.begin(chipSelect)) {
    Serial.println("Card failed, or not present");
    // don't do anything more:
  Serial.println("card initialized.");

void loop() {
  File myFile = SD.open("Data.txt", FILE_WRITE);
  if (myFile) {
    for (int i = 0; i < 101; i++) {
      myFile.print(" multiplied by two is ");
      myFile.println(i * 2, DEC);
  } else {
    Serial.println("Error opening Data.txt");
  //do nothing else
  do { } while(1);
  • I don't think it should matter, but can you try to close the file after opening and before the exists call? Jul 18, 2017 at 8:53
  • @MichelKeijzers Yes i tried it and it neither work Jul 18, 2017 at 8:59
  • You can try to format the card in a different format (I don't know which formats are supported by the library), also you can check if the file really is created (on a PC) or that the exists fails. Jul 18, 2017 at 10:03
  • @MichelKeijzers i do not why i open a new code file and copy the code and it worked. thanks for the help Jul 18, 2017 at 10:32
  • Glad you can continue now Jul 18, 2017 at 10:39

2 Answers 2

// open a new file and immediately close it:

Serial.println("Creating example.txt...");
myFile = SD.open("example.txt", FILE_WRITE);

This is what you missed (I guess..). Please see the link and check the steps followed:


If you want to make it sure it will not have problem with SD card format then format it to FAT it's most compatible format type.

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