SD println not working with ESP32

Other Hardware 3rd Party Boards
1

Im trying to use an SD card module with ESP32 but it seems that the function println is not working properly and is overwriting the data so it just keep the last data. Heres the code im using:

#include <SPI.h>
#include <SD.h>

const int chipSelect = 5;

int dat = 0;
String datstring = "";

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial);

  Serial.print("Initializing SD card...");

  // see if the card is present and can be initialized:
  if (!SD.begin(chipSelect)) {
    Serial.println("Card failed, or not present");
    // don't do anything more:
    while (1);
  }
  Serial.println("card initialized.");
}

void loop() {
    datstring = String(dat);
    File dataFile = SD.open("/datalog.txt", FILE_WRITE);
    if (dataFile) {
    dataFile.println(datstring);
    dataFile.close();
    // print to the serial port too:
    Serial.println(datstring);
    dat++;
  }else{Serial.println("ERRO-FILE");}
  delay(1000);

}

So in the archive it would be written a counting from line to line, like:
1
2
3
4
...
Buts its just keep the last number when i take de card or turn of the microcontroller. Heres the Serial monitor with verbose on:

Capturar

When it got to 8 I took the card and in the archive only have the number 8.
Someone can save me???

2

PS: I did a txt archive with random characters and make a code who just open and close the archive, dont write nothing. And the file content was just erased, so it the open file function mabe?
Heres the code:

#include <SPI.h>
#include <SD.h>
const int chipSelect = 5;

void setup() {
  Serial.begin(9600);
  while (!Serial);
  Serial.print("Initializing SD card...");
  if (!SD.begin(chipSelect)) {
    Serial.println("Card failed, or not present");
    while (1);
  }
  Serial.println("card initialized.");
  File dataFile = SD.open("/datalog.txt", FILE_WRITE);
    if (dataFile) {
    dataFile.close();
    }
  
}

void loop() {}
3

Your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for problems with (nor for advice on) your project.

4

Do this only once, in setup(), and close the file only when you are finished writing all data.

5

Thanks for the reply brother. So i can keep the file open indefinitely? But what if someone take the card off, isn't gonna corrupt the file?

6

I solved the problem, it seems that the ESP32 dont use the function SD.open like the arduino uno:

File dataFile = SD.open("/datalog.txt", FILE_APPEND);

If use "FILE_WRITE" it just clean all the data when opennig. Dont know why this happens but it works.

7

No, you have to close it sometime.

But what if someone take the card off, isn't gonna corrupt the file?

Of course it will. That happens with any computer. Your program should have a "stop recording" button or other means to close the file.