SD-kortmodul læse/skrive SPI

Arduino kode eksempel:

Arduino bibliotek

/*
 SD module example
 
 This example shows how to read and write data to and from an SD card file
 and 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 10
 
 created   Nov 2010
 by David A. Mellis
 updated 2 Dec 2010
 by Tom Igoe
 
 This example code is in the public domain.
      
 */
 
#include < SD.h >

// define the pin that powers up the SD card
#define MEM_PW 8

File myFile;

void setup()
{
  Serial.begin(9600);
  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.
 
  // on my MicroSD Module the power comes from a digital pin
  // I activate it at all times
   pinMode(MEM_PW, OUTPUT);
   digitalWrite(MEM_PW, HIGH);
  
  if (!SD.begin(10)) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");
 
  //delete old file
    SD.remove("example.txt");
   
  // 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.");
  }
 
  // open the file. note that only one file can be open at a time,
  // so you have to close this one before opening another.
  myFile = SD.open("example.txt", FILE_WRITE);
 
  // if the file opened okay, write to it:
  if (myFile) {
    Serial.print("Writing to example.txt...");
    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 example.txt");
  }
 
   // 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."); 
  }
 
  // re-open the file for reading:
  myFile = SD.open("example.txt");
  if (myFile) {
    Serial.println("example.txt:");
   
    // read from the file until there's nothing else in it:
    while (myFile.available()) {
        Serial.write(myFile.read());
    }
   
    //Delay to enable the user to stop the secuence
    Serial.println("if you want disconnect SD card ");
    delay(10000);
   
   
    // close the file:
    myFile.close();
  } else {
      // if the file didn't open, print an error:
    Serial.println("error opening example.txt");
  }
  // 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
}