Creating a file in an SD card

Question

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");
 }
 }

[Update]

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

#include <SD.h>
const int chipSelect = 10;
Sd2Card card;
void setup() {
 Serial.begin(115200);
 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:
 return;
 }
 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(i);
 myFile.print(" multiplied by two is ");
 myFile.println(i * 2, DEC);
 }
 Serial.println("Finished");
 myFile.close();
 } else {
 Serial.println("Error opening Data.txt");
 }
 //do nothing else
 do { } while(1);
}

• Michel Keijzers: I don't think it should matter, but can you try to close the file after opening and before the exists call?
• Miguel Sanz Narrillos: @MichelKeijzers Yes i tried it and it neither work
• Michel Keijzers: 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.
• Miguel Sanz Narrillos: @MichelKeijzers i do not why i open a new code file and copy the code and it worked. thanks for the help
• Michel Keijzers: Glad you can continue now

Answer 1

// open a new file and immediately close it:
Serial.println("Creating example.txt...");
myFile = SD.open("example.txt", FILE_WRITE);
myFile.close();

This is what you missed (I guess..). Please see the link and check the steps followed:
https://www.arduino.cc/en/Tutorial/Files

Answer 2

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.