SD card and file seek problem

[ESPfri2]

Hello
the following code end up with a read returning -1
I don't see what I am missing here ...
if you have ideas, thanks much !

Code: maib.cpp Select all

#include <Arduino.h>

#include <SPI.h>

#include <SD.h>

#include <errno.h>

#include <WiFi.h>

#include <time.h>

#include <sys/time.h>

#include <Wire.h>

#include <EEPROM.h>



struct Files_t {

	const char	*name;

	File	file;

};



struct Files_t f1 = { "/f1.txt"};

struct Files_t f2 = { "/f2.txt"};

struct Files_t f3 = { "/f3.txt"};



struct Files_t *Files[] = { &f1, &f2, &f3, NULL };



#define _BUFFERMAX 128

static char _Buffer[_BUFFERMAX]="";

char *LogPrintln ( const char * format, ... )

{

	va_list args;

	va_start (args, format);

	vsnprintf (_Buffer, _BUFFERMAX, format, (va_list)args);

	if (Serial) 

		Serial.println (_Buffer);

	va_end (args);

	return _Buffer;

}



void setup() {

  // Open serial communications and wait for port to open:

  Serial.begin(9600);



  delay(3000);

  while (!Serial) {

    ; // wait for serial port to connect. Needed for native USB port only

  }



  LogPrintln("Initializing SD card");



  if (!SD.begin(5)) {

    LogPrintln("... initialization failed");

    while (1);

  }

  LogPrintln("initialization done");



  LogPrintln("Openning file : %s", Files[0]->name);

  Files[0]->file = SD.open(Files[0]->name, FILE_WRITE);



  if (Files[0]->file) {

    LogPrintln("Writing to file : %s", Files[0]->name);

    Files[0]->file.println("line 1");

    Files[0]->file.println("line 2");

    Files[0]->file.println("line 3");

    Files[0]->file.println("line 4");

  } else 

    LogPrintln("error opening ");



  LogPrintln("Current Position : %d", Files[0]->file.position());

  Files[0]->file.flush();

  Files[0]->file.seek(0, SeekSet);

  LogPrintln("New Position   : %d", Files[0]->file.position());

  LogPrintln("Available data : %d", Files[0]->file.available());



  LogPrintln("Reading file ...");



  LogPrintln("%d", Files[0]->file.read());

  LogPrintln("%d %s", errno, strerror(errno));

//  while (Files[0]->file.available())

//    Serial.write(Files[0]->file.read());



}



void loop() {

  // put your main code here, to run repeatedly:

}

[igrr]

Could the file mode be an issue?

SD.open(Files[0]->name, FILE_WRITE);

To read and write a file, r+ or w+ modes should be used.

[ESPfri2]

in the file <FS.h> the only possible options for open are :

Code: Select all

namespace fs
{

#define FILE_READ       "r"
#define FILE_WRITE      "w"
#define FILE_APPEND     "a"

class File;

Here is the output of the above program :

initialization done
Openning file : /f1.txt
Writing to file : /f1.txt
Current Position : 32
New Position : 0
Available data : 32
Reading file
-1
9 Bad file number

everything looks fine except that read is not working as expected ...

[ESPfri2]

thanks @ESp_iggr

I switched to from FILE_WRITE to "a+" , and no more error ...