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One of the weak spot of the Arduinois the memory space. When playing with data (saving measurement, reading or writing to a file, etc.), it is necessary to have lot of space available. You can easily add memory to the Arduino with a Secure Digital card or SD card.

 

Material

  • Ordinateur
  • Arduino UNO x1
  • câble USB pour connecter l’Arduino à l’ordinateur x1
  • Shield ou module pour carte SD

 

SD Card module overview

Whatever the module you select. The idea is the same :  A slot for the SD card and some pins to interface the microcontroller with the SD card.

 

The SD card module has 6 pins to establish connection: 2 for power and 4 to establish a SPI connection (Serial Peripheral Interface).

  • 5V ou 3.3V for powering the module
  • GND for the ground
  • CS or ChipSelect to activate communication
  • MISO (Master Input, Slave Output) transmission pin, equivalent to Serial port pin Tx. Module output.
  • MOSI (Master Output, Slave Input) Reception pin equivalent to Serial port pin Rx. Module input.
  • SCK Clock to synchronise the devices

In case of a shield the wiring is predefined. Be sure to check the datasheet and to modify the code accordingly.

 

Wiring the SD card module

  • 3.3V on 3.3V
  • GND on GND
  • CS generally hooked up to 4 (here on10)
  • MISO generally on 12
  • MOSI generally on 11
  • SCK generally on 13

 

Code to get info on SD card

To interact with your SD card module or shield, there is a Arduino library : SD.h. Examples are available on the Arduino IDE.

// include the SD library:
#include <SPI.h>
#include <SD.h>
// set up variables using the SD utility library functions:
Sd2Card card;
SdVolume volume;
SdFile root;
// change this to match your SD shield or module;
// Arduino Ethernet shield: pin 4
// Adafruit SD shields and modules: pin 10
// Sparkfun SD shield: pin 8
// MKRZero SD: SDCARD_SS_PIN
// VELLEMAN I/O VMA304: SD shield: pin 10 
const int chipSelect = 10;
void setup() {
// Open serial communications and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}
Serial.print("\nInitializing SD card...");
// we'll use the initialization code from the utility libraries
// since we're just testing if the card is working!
if (!card.init(SPI_HALF_SPEED, chipSelect)) {
Serial.println("initialization failed. Things to check:");
Serial.println("* is a card inserted?");
Serial.println("* is your wiring correct?");
Serial.println("* did you change the chipSelect pin to match your shield or module?");
return;
} else {
Serial.println("Wiring is correct and a card is present.");
}
// print the type of card
Serial.print("\nCard type: ");
switch (card.type()) {
case SD_CARD_TYPE_SD1:
Serial.println("SD1");
break;
case SD_CARD_TYPE_SD2:
Serial.println("SD2");
break;
case SD_CARD_TYPE_SDHC:
Serial.println("SDHC");
break;
default:
Serial.println("Unknown");
}
// Now we will try to open the 'volume'/'partition' - it should be FAT16 or FAT32
if (!volume.init(card)) {
Serial.println("Could not find FAT16/FAT32 partition.\nMake sure you've formatted the card");
return;
}
// print the type and size of the first FAT-type volume
uint32_t volumesize;
Serial.print("\nVolume type is FAT");
Serial.println(volume.fatType(), DEC);
Serial.println();
volumesize = volume.blocksPerCluster();    // clusters are collections of blocks
volumesize *= volume.clusterCount();       // we'll have a lot of clusters
volumesize *= 512;                            // SD card blocks are always 512 bytes
Serial.print("Volume size (bytes): ");
Serial.println(volumesize);
Serial.print("Volume size (Kbytes): ");
volumesize /= 1024;
Serial.println(volumesize);
Serial.print("Volume size (Mbytes): ");
volumesize /= 1024;
Serial.println(volumesize);
Serial.println("\nFiles found on the card (name, date and size in bytes): ");
root.openRoot(volume);
// list all files in the card with date and size
root.ls(LS_R | LS_DATE | LS_SIZE);
}
void loop(void) {
}

Code to read or wirte a file on the SD card

/*
  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 (for MKRZero SD: SDCARD_SS_PIN)
 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;
const int chipSelect = 10;
void setup() {
// Open serial communications and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}
Serial.print("Initializing SD card...");
if (!SD.begin(chipSelect)) {
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
}

 

Test and mix those examples to get the functionality that you want. If you have any issue interacting with your SD card module. Do not hesitate to let a comment or to send us a message.

 

Application

Add memory to your robots

Give voice to your robot

 

Source

THE Arduino reference

Seeed Stufio SD Card shield V4.0