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Using the SD library to create and remove files on a SD card

This example shows how to create and destroy a file on a SD card. Please click here for more information on the SD library.

Hardware Required

  • Arduino board
  • Ethernet Shield (or other board with an SD slot)
  • Formatted SD card

Circuit

image developed using Fritzing. For more circuit examples, see the Fritzing project page

None, but the Arduino has to have the Ethernet Shield and a USB cable connected to the computer.

Code

The code below is configured for use with an Ethernet shield, which has an onboard SD slot. In the setup(), SD.begin() names pin 4 as the CS pin. This pin varies depending on the make of shield or board you are using.

In the setup(), open a new file with SD.open() named "example.txt". FILE_WRITE enables read and write access to the file, starting at the end. In this example though, immediately close the file by calling myFile.close().

After checking to make sure the file exists with SD.exists(), delete the file from the card with SD.remove.

/*
  SD card basic file example
 
 This example shows how to create and destroy an SD card file  
 The circuit:
 * SD card attached to SPI bus as follows:
 ** MOSI - pin 11
 ** MISO - pin 12
 ** CLK - pin 13
 ** CS - pin 4
 
 created   Nov 2010
 by David A. Mellis
 modified 9 Apr 2012
 by Tom Igoe
 
 This example code is in the public domain.
     
 */

#include <SD.h>

File myFile;

void setup()
{
 // Open serial communications and wait for port to open:
  Serial.begin(9600);
   while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }


  Serial.print("Initializing SD card...");
  // On the Ethernet Shield, CS is pin 4. It's set as an output by default.
  // Note that even if it's not used as the CS pin, the hardware SS pin
  // (10 on most Arduino boards, 53 on the Mega) must be left as an output
  // or the SD library functions will not work.
  pinMode(10, OUTPUT);

  if (!SD.begin(4)) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");

  if (SD.exists("example.txt")) {
    Serial.println("example.txt exists.");
  }
  else {
    Serial.println("example.txt doesn't exist.");
  }

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

  // Check to see if the file exists:
  if (SD.exists("example.txt")) {
    Serial.println("example.txt exists.");
  }
  else {
    Serial.println("example.txt doesn't exist.");  
  }

  // delete the file:
  Serial.println("Removing example.txt...");
  SD.remove("example.txt");

  if (SD.exists("example.txt")){
    Serial.println("example.txt exists.");
  }
  else {
    Serial.println("example.txt doesn't exist.");  
  }
}

void loop()
{
  // nothing happens after setup finishes.
}

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