Utilizzare una scheda SD su Arduino tramite la libreria SD

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In questo articolo sarà esposto un tutorial su come utilizzare una scheda SD per implementare vari sketch e librerie. Per fare ciò si utilizza una libreria che consente di leggere e scrivere su schede SD.

Per la riuscita di questo progetto basta utilizzare una scheda Arduino o Genuino, un Ethernet Shield (o una qualsiasi altre board dotata di uno slot per le SD card) e una scheda SD formattata.

La board di Arduino o Genuino deve essere collegata sia all’Ethernet Shield sia al computer, tramite l’ausilio del cavo USB.

Di seguito è riportato lo sketch per eseguire la lettura/scrittura da scheda SD tramite l’ausilio della libreria SD. Tale sketch proviene dal sito ufficiale arduino.cc (clicca qui).

/*
  SD card read/write
 
 This example shows how to read and write data to and from 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 <SPI.h>
#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.");
  
  // 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("test.txt", FILE_WRITE);
  
  // if the file opened okay, write to it:
  if (myFile) {
    Serial.print("Writing to test.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 test.txt");
  }
  
  // re-open the file for reading:
  myFile = SD.open("test.txt");
  if (myFile) {
    Serial.println("test.txt:");
    
    // 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");
  }
}

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

SD card read/write

This example shows how to read and write data to and from 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 <SPI.h>

#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.");

// 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("test.txt", FILE_WRITE);

// if the file opened okay, write to it:

if (myFile) {

Serial.print("Writing to test.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 test.txt");

}

// re-open the file for reading:

myFile = SD.open("test.txt");

if (myFile) {

Serial.println("test.txt:");

// 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");

}

void loop()

{

// nothing happens after setup

}

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