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: [Select all] [Expand/Collapse]

1. #include <Arduino.h>
2. #include <SPI.h>
3. #include <SD.h>
4. #include <errno.h>
5. #include <WiFi.h>
6. #include <time.h>
7. #include <sys/time.h>
8. #include <Wire.h>
9. #include <EEPROM.h>
10.  
11. struct Files_t {
12.     const char  *name;
13.     File    file;
14. };
15.  
16. struct Files_t f1 = { "/f1.txt"};
17. struct Files_t f2 = { "/f2.txt"};
18. struct Files_t f3 = { "/f3.txt"};
19.  
20. struct Files_t *Files[] = { &f1, &f2, &f3, NULL };
21.  
22. #define _BUFFERMAX 128
23. static char _Buffer[_BUFFERMAX]="";
24. char *LogPrintln ( const char * format, ... )
25. {
26.     va_list args;
27.     va_start (args, format);
28.     vsnprintf (_Buffer, _BUFFERMAX, format, (va_list)args);
29.     if (Serial)
30.         Serial.println (_Buffer);
31.     va_end (args);
32.     return _Buffer;
33. }
34.  
35. void setup() {
36.   // Open serial communications and wait for port to open:
37.   Serial.begin(9600);
38.  
39.   delay(3000);
40.   while (!Serial) {
41.     ; // wait for serial port to connect. Needed for native USB port only
42.   }
43.  
44.   LogPrintln("Initializing SD card");
45.  
46.   if (!SD.begin(5)) {
47.     LogPrintln("... initialization failed");
48.     while (1);
49.   }
50.   LogPrintln("initialization done");
51.  
52.   LogPrintln("Openning file : %s", Files[0]->name);
53.   Files[0]->file = SD.open(Files[0]->name, FILE_WRITE);
54.  
55.   if (Files[0]->file) {
56.     LogPrintln("Writing to file : %s", Files[0]->name);
57.     Files[0]->file.println("line 1");
58.     Files[0]->file.println("line 2");
59.     Files[0]->file.println("line 3");
60.     Files[0]->file.println("line 4");
61.   } else
62.     LogPrintln("error opening ");
63.  
64.   LogPrintln("Current Position : %d", Files[0]->file.position());
65.   Files[0]->file.flush();
66.   Files[0]->file.seek(0, SeekSet);
67.   LogPrintln("New Position   : %d", Files[0]->file.position());
68.   LogPrintln("Available data : %d", Files[0]->file.available());
69.  
70.   LogPrintln("Reading file ...");
71.  
72.   LogPrintln("%d", Files[0]->file.read());
73.   LogPrintln("%d %s", errno, strerror(errno));
74. //  while (Files[0]->file.available())
75. //    Serial.write(Files[0]->file.read());
76.  
77. }
78.  
79. void loop() {
80.   // put your main code here, to run repeatedly:
81. }

GeSHi © Codebox Plus Extension

[ESP_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 ...