Guardar archivo con arduino

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

const int chipSelect = 4;

void setup()
{
Serial.begin(9600);
pinMode(10, OUTPUT);

if (!SD.begin(chipSelect)) {
Serial.println("initialization failed!");
return;
}
Serial.println("initialization done.");
}

void loop()
{
Serial.println("I'm writing to the file");

// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
File myFile = SD.open("test.txt", FILE_WRITE);

// if the file opened okay, write to it:
if (myFile) {
myFile.println("testing 1, 2, 3.");
// close the file:
myFile.close();
Serial.println("done.");
} else {
// if the file didn't open, print an error:
Serial.println("error opening test.txt");
}

// re-open the file for reading:
myFile = SD.open("test.txt");
if (myFile) {
// read from the file until there's nothing else in it:
while (myFile.available()) {
Serial.write(myFile.read());
}
// close the file:
myFile.close();
} else {
// if the file didn't open, print an error:
Serial.println("error opening test.txt");
}

// delete the file:
SD.remove("test.txt");

// re-open the file for reading:
myFile = SD.open("test.txt");
if (myFile) {
Serial.println("test.txt exists");
} else {
Serial.println("test.txt doesn't exist- it has been deleted.");
}

delay(5000);
}