Can't read SD card

Question

I get errors to open file on SD card. This is the instructions I use https://www.instructables.com/Micro-SD-Card-Tutorial/

/*
  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;

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(4)) {
    Serial.println("initialization failed!");
    while (1);
  }
  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
}

I see "Initializing SD card..." and "initialization done." and "error opening test.txt"

Can you help me to solve problem?

run the CardInfo example. it is a diagnostic tool

Juraj
– Juraj ♦

2024-07-14 09:35:01 +00:00
Commented Jul 14, 2024 at 9:35 — Juraj
– Juraj ♦, Commented Jul 14, 2024 at 9:35
Had you formatted the card in FAT32?

fabianoriccardi
– fabianoriccardi

2024-07-14 13:26:19 +00:00
Commented Jul 14, 2024 at 13:26 — fabianoriccardi
– fabianoriccardi, Commented Jul 14, 2024 at 13:26

Lee-xp · Accepted Answer · 2024-07-14 09:19:15Z

I ran your code unchanged on an Arduino Uno, and it worked first time. It output:

Initializing SD card...initialization done.
Writing to test.txt...done.
test.txt:
testing 1, 2, 3.

So your problem is either to do with the SD card itself or your connections to the board (or I suppose the SD card board could be faulty). For the card, make sure that it is formatted with FAT16 or FAT32. Mine is FAT32, and check that you can read and write to it using a PC - just drop a text file onto it to Write, and double click the text file to Read.

For the connections there is not really much to go wrong. Just check your wiring. And for the supply I used the 5v from the Arduino board.

Gil Sven · Accepted Answer · 2024-07-17 16:47:21Z

I added some delays to the code and it work perfectly now.

/*
  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;

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(4)) {
    Serial.println("initialization failed!");
    while (1);
  }
  Serial.println("initialization done.");
  delay(1000);

  // 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);
  delay(1000);

  // 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
}

your CS pins is not wired correctly if delays somehow help. it should work without the delays. — Juraj
– Juraj ♦, Commented Jul 17, 2024 at 16:55

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