Filenames need to be absolute. Start with a slash.

Thank you very much, That solved it. I didn't know that before. With Arduino boards I never used the slash.

Hi,
I want to use my ESP32 board to write on my SD card. using the example that comes with the esp32 board package, all things are OK. But when I wrote my own code, It can not open the file to write in it.

#include "FS.h"
#include "SD.h"
#include "SPI.h"


bool sdInitSuccess = false;
#define ...