I am using Wemos Mini ESP8266 and trying to make control panel on this platform. But i have stuck when it needs to save data to a file.

Tried to using LittleFS method to save json to file, still causes crashing.

Here is my code:

#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <Wire.h>
#include <LittleFS.h>
#include <ArduinoJson.h>
#include <Arduino.h>

const char* ssid = "wifi01";
const char* password = "password01";
const char *dataFile = "/data.json";

unsigned long last_save = 0;

ESP8266WebServer server(80);

void handleRoot() {
  server.send(200, "text/plain", "Index page");
}

bool saveData() {
  LittleFS.begin();
  StaticJsonDocument<200> doc;
  doc["foo"] = 10;
  doc["bar"] = 50;

  File data = LittleFS.open(dataFile, "w");
  serializeJson(doc, data);
  LittleFS.end();
  return true;
}

void setup(void) {

  Serial.begin(9600);

  WiFi.mode(WIFI_AP);
  WiFi.softAP(ssid, password);

  IPAddress myIP = WiFi.softAPIP();

  server.on("/", handleRoot);

  server.begin();
  Serial.println("Server started");
  last_save = millis();
}

void loop(void) {
  server.handleClient();
  if(millis() - last_save > 5000){
    saveData();
  }
}

Here is an exception stack

Exception (3):
epc1=0x4010076d epc2=0x00000000 epc3=0x00000000 excvaddr=0x4006f441 depc=0x00000000

>>>stack>>>

ctx: cont
sp: 3ffffcc0 end: 3fffffd0 offset: 0150
3ffffe10:  402021dc 3ffffe20 ffffffff 00002000  
3ffffe20:  00000040 3ffef8fc 00000020 401009f4  
3ffffe30:  00000000 00000001 3ffef884 40202a3c  
3ffffe40:  0000ef6f 00000001 3ffefc36 3ffef884  
3ffffe50:  3ffeea44 3ffef884 3ffef87c 40204a1f  
3ffffe60:  00000008 3ffffed0 37400000 402044fc  
3ffffe70:  00000000 00000001 00000003 000011c0  
3ffffe80:  500ffc30 00010002 ffffffff ffffffff  
3ffffe90:  37400408 3ffffed0 00000005 00000005  
3ffffea0:  000007e0 000000fc 3ffe85ec 40100672  
3ffffeb0:  00000a80 00000150 3ffe85ec 40100672  
3ffffec0:  00000988 00000131 3ffe85ec 40100672  
3ffffed0:  00000cb8 00000197 3ffe85ec 3ffeeb54  
3ffffee0:  3ffeea44 3ffef884 3ffef87c 4020a97d  
3ffffef0:  3fffff1c 00000000 3ffef87c 4020aa7c  
3fffff00:  3ffeea44 00000000 3ffeeb28 402085b6  
3fffff10:  3ffe85d4 3fffda00 00000000 00000000  
3fffff20:  00000000 feefeffe feefeffe feefeffe  
3fffff30:  40207d0c feefeffe 40210584 40209f36  
3fffff40:  00040000 feefffff 00030000 ffff0020  
3fffff50:  402114e8 3fffff70 00000001 402109dc  
3fffff60:  3fffdad0 00000000 3ffee7f0 4020898d  
3fffff70:  4021126c 00000000 00001388 3fffff50  
3fffff80:  00000000 00001461 970a3d70 001790d6  
3fffff90:  00000000 00000000 feefeffe 3ffeeb54  
3fffffa0:  3fffdad0 00000000 3ffeeb28 3ffeeb54  
3fffffb0:  3fffdad0 00000000 3ffeeb28 4020e2c8  
3fffffc0:  feefeffe feefeffe 3fffdab0 40100c99  
<<<stack<<<

And here is decoded exception

Exception 3: LoadStoreError: Processor internal physical address or data error during load or store
PC: 0x4010076d
EXCVADDR: 0x4006f441

Decoding stack results
0x402021dc: lfs_dir_find_match at c:\users\������\appdata\local\arduino15\packages\esp8266\hardware\esp8266\3.1.2\libraries\littlefs\lib\littlefs/lfs.c line 1296
0x401009f4: malloc(size_t) at C:\Users\������\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.1.2\cores\esp8266\umm_malloc\umm_malloc.cpp line 912
0x40202a3c: lfs_init at c:\users\������\appdata\local\arduino15\packages\esp8266\hardware\esp8266\3.1.2\libraries\littlefs\lib\littlefs/lfs_util.h line 221
0x40204a1f: lfs_mount at c:\users\������\appdata\local\arduino15\packages\esp8266\hardware\esp8266\3.1.2\libraries\littlefs\lib\littlefs/lfs.c line 4097
0x402044fc: lfs_commitattr at c:\users\������\appdata\local\arduino15\packages\esp8266\hardware\esp8266\3.1.2\libraries\littlefs\lib\littlefs/lfs.c line 3880
0x40100672: umm_free_core(umm_heap_context_t*, void*) at C:\Users\������\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.1.2\cores\esp8266\umm_malloc\umm_malloc.cpp line 642
0x40100672: umm_free_core(umm_heap_context_t*, void*) at C:\Users\������\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.1.2\cores\esp8266\umm_malloc\umm_malloc.cpp line 642
0x40100672: umm_free_core(umm_heap_context_t*, void*) at C:\Users\������\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.1.2\cores\esp8266\umm_malloc\umm_malloc.cpp line 642
0x4020a97d: littlefs_impl::LittleFSImpl::_tryMount() at C:\Users\������\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.1.2\libraries\LittleFS\src/LittleFS.h line 285
0x4020aa7c: littlefs_impl::LittleFSImpl::begin() at C:\Users\������\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.1.2\libraries\LittleFS\src/LittleFS.h line 193
0x402085b6: saveData() at C:\Users\������\Documents\Arduino\libraries\ArduinoJson\src/ArduinoJson/Memory/ResourceManager.hpp line 31
0x40207d0c: handleRoot() at C:\Users\������\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.1.2\libraries\ESP8266WebServer\src/ESP8266WebServer-impl.h line 518
0x40210584: std::_Function_handler ::_M_manager(std::_Any_data&, std::_Any_data const&, std::_Manager_operation) at c:\users\������\appdata\local\arduino15\packages\esp8266\tools\xtensa-lx106-elf-gcc\3.1.0-gcc10.3-e5f9fec\xtensa-lx106-elf\include\c++\10.3.0\bits/std_function.h line 268
0x40209f36: WiFiServer::accept() at C:\Users\������\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.1.2\libraries\ESP8266WiFi\src\WiFiServer.cpp line 151
0x402109dc: WiFiClient::operator bool() at C:\Users\������\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.1.2\libraries\ESP8266WiFi\src\WiFiClient.cpp line 342
0x4020898d: esp8266webserver::ESP8266WebServerTemplate ::handleClient() at C:\Users\������\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.1.2\libraries\ESP8266WebServer\src/ESP8266WebServer-impl.h line 282
0x4020e2c8: loop_wrapper() at C:\Users\������\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.1.2\cores\esp8266\core_esp8266_main.cpp line 258

I have readed about every forum to solve the problem, but it gave nothing.