Root.ls works for me but SD.exists doesn't

Other Hardware Storage
1

Hi All,

I have an OLED screen with a micro SD card slot

and I want to read images from the card and display them on the screen.

I can’t seem to get the Arduino to read the card.

Sort of.

I have tried FAT-16 and FAT-32 cards.

I have tried Micro 32GB cards and full size, old school 32Mb cards.

I have tried using the card onboard the OLED screen. I have tried using a separate SD card shield.

I have tried two different Arduinos (Elegoo & Hero)

Same result with all of them. I can get the directory with root.ls but I cannot open any files with SD.open or SD.exists

My test code:

/*
  SD card test

  This example shows how use the utility libraries on which the'
  SD library is based in order to get info about your SD card.
  Very useful for testing a card when you're not sure whether its working or not.

  The circuit:
    SD card attached to SPI bus as follows:
 ** MOSI - pin 11 on Arduino Uno/Duemilanove/Diecimila
 ** MISO - pin 12 on Arduino Uno/Duemilanove/Diecimila
 ** CLK - pin 13 on Arduino Uno/Duemilanove/Diecimila
 ** CS - depends on your SD card shield or module.
     Pin 4 used here for consistency with other Arduino examples


  created  28 Mar 2011
  by Limor Fried
  modified 9 Apr 2012
  by Tom Igoe
*/
// 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
int chipSelect = 10;

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
  }


  // 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?");
      Serial.println(chipSelect);
    Serial.println("");
  } else {
    Serial.println("Wiring is correct and a card is present.");
  }



  // print the type of card
  Serial.println();
  Serial.print("Card 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");
    while (1);
  }

  Serial.print("Clusters:          ");
  Serial.println(volume.clusterCount());
  Serial.print("Blocks x Cluster:  ");
  Serial.println(volume.blocksPerCluster());

  Serial.print("Total Blocks:      ");
  Serial.println(volume.blocksPerCluster() * volume.clusterCount());
  Serial.println();

  // print the type and size of the first FAT-type volume
  uint32_t volumesize;
  Serial.print("Volume type is:    FAT");
  Serial.println(volume.fatType(), DEC);

  volumesize = volume.blocksPerCluster();    // clusters are collections of blocks
  volumesize *= volume.clusterCount();       // we'll have a lot of clusters
  volumesize /= 2;                           // SD card blocks are always 512 bytes (2 blocks are 1KB)
  Serial.print("Volume size (Kb):  ");
  Serial.println(volumesize);
  Serial.print("Volume size (Mb):  ");
  volumesize /= 1024;
  Serial.println(volumesize);
  Serial.print("Volume size (Gb):  ");
  Serial.println((float)volumesize / 1024.0);

  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);

  if (SD.exists("TEST.TXT")){
     Serial.println("SD.exists found TEST.TXT");}

  else {Serial.println("SD.exists failed to find TEST.TXT");}
     
  
  // re-open the file for reading:
  myFile = SD.open("TEST.TXT");
  if (myFile) {
    Serial.println("SD.open failed to create 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("SD.open failed to create TEST.TXT");
  }
}

void loop(void) {
}

This is the output I get:

10:38:08.197 -> Wiring is correct and a card is present.
10:38:08.244 ->
10:38:08.244 -> Card type: SD1
10:38:08.292 -> Clusters: 60237
10:38:08.292 -> Blocks x Cluster: 1
10:38:08.292 -> Total Blocks: 60237
10:38:08.338 ->
10:38:08.338 -> Volume type is: FAT16
10:38:08.384 -> Volume size (Kb): 30118
10:38:08.384 -> Volume size (Mb): 29
10:38:08.384 -> Volume size (Gb): 0.03
10:38:08.431 ->
10:38:08.431 -> Files found on the card (name, date and size in bytes):
10:38:08.524 -> SYSTEM~1/ 2023-06-30 16:43:04
10:38:08.524 -> WPSETT~1.DAT 2023-06-30 16:43:04 12
10:38:08.571 -> INDEXE~1 2023-06-30 16:43:06 76
10:38:08.616 -> TEST.TXT 2023-06-30 16:54:36 584
10:38:08.663 -> SD.exists failed to find TEST.TXT
10:38:08.710 -> SD.open failed to create TEST.TXT

Any thoughts?

Cheers,

Wilson.

2

Instead of using SD.open("TEST.TXT"), try using SD.open("/TEST.TXT")

3

Thanks for the suggestion!

I was hoping it would be something stupid (and it probably actually is) but sadly, adding ‘/’ did not change anything.

image001.png1697×858 54.7 KB

4

I see...

  1. verify the File Path: make sure that the file "TEST.TXT" is located in the root directory of the SD card.
  2. check the filename sensitivity: try : test.txt
5

Well… this is interesting… although root.ls identifies the file as” TEXT.TXT” it is in fact “test.txt”

image001.png1103×638 14.9 KB

However, changing the file name to “test.txt” seems to have had no effect.

image002.png1772×935 59.4 KB

6

Is this possibly a permissions thing?

I have permissions to list the root directory but NOT permissions to use SD ?

Are permissions even a thing on Arduinos?

7

Try this:

 if (SD.chmod("test.txt", FILE_WRITE)) {
      Serial.println("Changed file permissions successfully.");
    } else {
      Serial.println("Failed to change file permissions.");
    }
8

OK, either chmod isn’t a thing on Arduinos or my version of the SD lib does not have it.

image001.png1062×997 40 KB

9

OK, I purchased a MKR ZERO with onboard SD card.

I used the same micro SD card from previous experiments (32GB Fat-32) and... it works.

Using the same code but compiled for SAMD.

10

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