[GH-ISSUE #1572] ESP32-S2 failed to open config file or writing

kerem commented

2026-02-28 01:29:40 +03:00

Owner

Originally created by @xpeqex on GitHub (Mar 9, 2023).
Original GitHub issue: https://github.com/tzapu/WiFiManager/issues/1572

WiFimanager 2.0.15-rc.1
Esp32-S2
Core Version: 2.0.7

Description

Using the example AutoConnectWithFSParameters the sketch is unable to open the config file for writing (/config.json). The configurations are saved the first time, but when the micro is restarted the parameter settings are lost, the WiFi credentials are kept.

Settings in IDE

Module: ESP32 Dev Module
USB CDC On Boot Enable
USB DFU On Boot disbaled
Additional libraries:

Sketch

#include <WiFiManager.h>          //https://github.com/tzapu/WiFiManager

#ifdef ESP32
  #include <SPIFFS.h>
#endif

#include <ArduinoJson.h>          //https://github.com/bblanchon/ArduinoJson

//define your default values here, if there are different values in config.json, they are overwritten.
char mqtt_server[40];
char mqtt_port[6] = "8080";
char api_token[34] = "YOUR_API_TOKEN";

//flag for saving data
bool shouldSaveConfig = false;

//callback notifying us of the need to save config
void saveConfigCallback () {
  Serial.println("Should save config");
  shouldSaveConfig = true;
}

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println();

  //clean FS, for testing
  //SPIFFS.format();

  //read configuration from FS json
  Serial.println("mounting FS...");

  if (SPIFFS.begin()) {
    Serial.println("mounted file system");
    if (SPIFFS.exists("/config.json")) {
      //file exists, reading and loading
      Serial.println("reading config file");
      File configFile = SPIFFS.open("/config.json", "r");
      if (configFile) {
        Serial.println("opened config file");
        size_t size = configFile.size();
        // Allocate a buffer to store contents of the file.
        std::unique_ptr<char[]> buf(new char[size]);

        configFile.readBytes(buf.get(), size);

 #if defined(ARDUINOJSON_VERSION_MAJOR) && ARDUINOJSON_VERSION_MAJOR >= 6
        DynamicJsonDocument json(1024);
        auto deserializeError = deserializeJson(json, buf.get());
        serializeJson(json, Serial);
        if ( ! deserializeError ) {
#else
        DynamicJsonBuffer jsonBuffer;
        JsonObject& json = jsonBuffer.parseObject(buf.get());
        json.printTo(Serial);
        if (json.success()) {
#endif
          Serial.println("\nparsed json");
          strcpy(mqtt_server, json["mqtt_server"]);
          strcpy(mqtt_port, json["mqtt_port"]);
          strcpy(api_token, json["api_token"]);
        } else {
          Serial.println("failed to load json config");
        }
        configFile.close();
      }
    }
  } else {
    Serial.println("failed to mount FS");
  }
  //end read

  // The extra parameters to be configured (can be either global or just in the setup)
  // After connecting, parameter.getValue() will get you the configured value
  // id/name placeholder/prompt default length
  WiFiManagerParameter custom_mqtt_server("server", "mqtt server", mqtt_server, 40);
  WiFiManagerParameter custom_mqtt_port("port", "mqtt port", mqtt_port, 6);
  WiFiManagerParameter custom_api_token("apikey", "API token", api_token, 32);

  //WiFiManager
  //Local intialization. Once its business is done, there is no need to keep it around
  WiFiManager wifiManager;

  //set config save notify callback
  wifiManager.setSaveConfigCallback(saveConfigCallback);

  //set static ip
  wifiManager.setSTAStaticIPConfig(IPAddress(10, 0, 1, 99), IPAddress(10, 0, 1, 1), IPAddress(255, 255, 255, 0));

  //add all your parameters here
  wifiManager.addParameter(&custom_mqtt_server);
  wifiManager.addParameter(&custom_mqtt_port);
  wifiManager.addParameter(&custom_api_token);

  //reset settings - for testing
  //wifiManager.resetSettings();

  //set minimu quality of signal so it ignores AP's under that quality
  //defaults to 8%
  //wifiManager.setMinimumSignalQuality();

  //sets timeout until configuration portal gets turned off
  //useful to make it all retry or go to sleep
  //in seconds
  //wifiManager.setTimeout(120);

  //fetches ssid and pass and tries to connect
  //if it does not connect it starts an access point with the specified name
  //here  "AutoConnectAP"
  //and goes into a blocking loop awaiting configuration
  if (!wifiManager.autoConnect("AutoConnectAP", "password")) {
    Serial.println("failed to connect and hit timeout");
    delay(3000);
    //reset and try again, or maybe put it to deep sleep
    ESP.restart();
    delay(5000);
  }

  //if you get here you have connected to the WiFi
  Serial.println("connected...yeey :)");

  //read updated parameters
  strcpy(mqtt_server, custom_mqtt_server.getValue());
  strcpy(mqtt_port, custom_mqtt_port.getValue());
  strcpy(api_token, custom_api_token.getValue());
  Serial.println("The values in the file are: ");
  Serial.println("\tmqtt_server : " + String(mqtt_server));
  Serial.println("\tmqtt_port : " + String(mqtt_port));
  Serial.println("\tapi_token : " + String(api_token));

  //save the custom parameters to FS
  if (shouldSaveConfig) {
    Serial.println("saving config");
 #if defined(ARDUINOJSON_VERSION_MAJOR) && ARDUINOJSON_VERSION_MAJOR >= 6
    DynamicJsonDocument json(1024);
#else
    DynamicJsonBuffer jsonBuffer;
    JsonObject& json = jsonBuffer.createObject();
#endif
    json["mqtt_server"] = mqtt_server;
    json["mqtt_port"] = mqtt_port;
    json["api_token"] = api_token;

    File configFile = SPIFFS.open("/config.json", "w");
    if (!configFile) {
      Serial.println("failed to open config file for writing");
    }

#if defined(ARDUINOJSON_VERSION_MAJOR) && ARDUINOJSON_VERSION_MAJOR >= 6
    serializeJson(json, Serial);
    serializeJson(json, configFile);
#else
    json.printTo(Serial);
    json.printTo(configFile);
#endif
    configFile.close();
    //end save
  }

  Serial.println("local ip");
  Serial.println(WiFi.localIP());
}

void loop() {
  // put your main code here, to run repeatedly:

}

Debug Messages

The values in the file are: 
12:13:58.156 -> 	mqtt_server : google.com
12:13:58.156 -> 	mqtt_port : 8080
12:13:58.156 -> 	api_token : 22
12:13:58.156 -> saving config
12:13:58.156 -> failed to open config file for writing
12:13:58.156 -> {"mqtt_server":"google.com","mqtt_port":"8080","api_token":"22"}local ip
12:13:58.156 -> 10.0.1.99```

Originally created by @xpeqex on GitHub (Mar 9, 2023). Original GitHub issue: https://github.com/tzapu/WiFiManager/issues/1572 WiFimanager 2.0.15-rc.1 Esp32-S2 Core Version: 2.0.7 ### Description Using the example AutoConnectWithFSParameters the sketch is unable to open the config file for writing (/config.json). The configurations are saved the first time, but when the micro is restarted the parameter settings are lost, the WiFi credentials are kept. ### Settings in IDE Module: ESP32 Dev Module USB CDC On Boot Enable USB DFU On Boot disbaled Additional libraries: ### Sketch ```#include <FS.h> //this needs to be first, or it all crashes and burns... #include <WiFiManager.h> //https://github.com/tzapu/WiFiManager #ifdef ESP32 #include <SPIFFS.h> #endif #include <ArduinoJson.h> //https://github.com/bblanchon/ArduinoJson //define your default values here, if there are different values in config.json, they are overwritten. char mqtt_server[40]; char mqtt_port[6] = "8080"; char api_token[34] = "YOUR_API_TOKEN"; //flag for saving data bool shouldSaveConfig = false; //callback notifying us of the need to save config void saveConfigCallback () { Serial.println("Should save config"); shouldSaveConfig = true; } void setup() { // put your setup code here, to run once: Serial.begin(115200); Serial.println(); //clean FS, for testing //SPIFFS.format(); //read configuration from FS json Serial.println("mounting FS..."); if (SPIFFS.begin()) { Serial.println("mounted file system"); if (SPIFFS.exists("/config.json")) { //file exists, reading and loading Serial.println("reading config file"); File configFile = SPIFFS.open("/config.json", "r"); if (configFile) { Serial.println("opened config file"); size_t size = configFile.size(); // Allocate a buffer to store contents of the file. std::unique_ptr<char[]> buf(new char[size]); configFile.readBytes(buf.get(), size); #if defined(ARDUINOJSON_VERSION_MAJOR) && ARDUINOJSON_VERSION_MAJOR >= 6 DynamicJsonDocument json(1024); auto deserializeError = deserializeJson(json, buf.get()); serializeJson(json, Serial); if ( ! deserializeError ) { #else DynamicJsonBuffer jsonBuffer; JsonObject& json = jsonBuffer.parseObject(buf.get()); json.printTo(Serial); if (json.success()) { #endif Serial.println("\nparsed json"); strcpy(mqtt_server, json["mqtt_server"]); strcpy(mqtt_port, json["mqtt_port"]); strcpy(api_token, json["api_token"]); } else { Serial.println("failed to load json config"); } configFile.close(); } } } else { Serial.println("failed to mount FS"); } //end read // The extra parameters to be configured (can be either global or just in the setup) // After connecting, parameter.getValue() will get you the configured value // id/name placeholder/prompt default length WiFiManagerParameter custom_mqtt_server("server", "mqtt server", mqtt_server, 40); WiFiManagerParameter custom_mqtt_port("port", "mqtt port", mqtt_port, 6); WiFiManagerParameter custom_api_token("apikey", "API token", api_token, 32); //WiFiManager //Local intialization. Once its business is done, there is no need to keep it around WiFiManager wifiManager; //set config save notify callback wifiManager.setSaveConfigCallback(saveConfigCallback); //set static ip wifiManager.setSTAStaticIPConfig(IPAddress(10, 0, 1, 99), IPAddress(10, 0, 1, 1), IPAddress(255, 255, 255, 0)); //add all your parameters here wifiManager.addParameter(&custom_mqtt_server); wifiManager.addParameter(&custom_mqtt_port); wifiManager.addParameter(&custom_api_token); //reset settings - for testing //wifiManager.resetSettings(); //set minimu quality of signal so it ignores AP's under that quality //defaults to 8% //wifiManager.setMinimumSignalQuality(); //sets timeout until configuration portal gets turned off //useful to make it all retry or go to sleep //in seconds //wifiManager.setTimeout(120); //fetches ssid and pass and tries to connect //if it does not connect it starts an access point with the specified name //here "AutoConnectAP" //and goes into a blocking loop awaiting configuration if (!wifiManager.autoConnect("AutoConnectAP", "password")) { Serial.println("failed to connect and hit timeout"); delay(3000); //reset and try again, or maybe put it to deep sleep ESP.restart(); delay(5000); } //if you get here you have connected to the WiFi Serial.println("connected...yeey :)"); //read updated parameters strcpy(mqtt_server, custom_mqtt_server.getValue()); strcpy(mqtt_port, custom_mqtt_port.getValue()); strcpy(api_token, custom_api_token.getValue()); Serial.println("The values in the file are: "); Serial.println("\tmqtt_server : " + String(mqtt_server)); Serial.println("\tmqtt_port : " + String(mqtt_port)); Serial.println("\tapi_token : " + String(api_token)); //save the custom parameters to FS if (shouldSaveConfig) { Serial.println("saving config"); #if defined(ARDUINOJSON_VERSION_MAJOR) && ARDUINOJSON_VERSION_MAJOR >= 6 DynamicJsonDocument json(1024); #else DynamicJsonBuffer jsonBuffer; JsonObject& json = jsonBuffer.createObject(); #endif json["mqtt_server"] = mqtt_server; json["mqtt_port"] = mqtt_port; json["api_token"] = api_token; File configFile = SPIFFS.open("/config.json", "w"); if (!configFile) { Serial.println("failed to open config file for writing"); } #if defined(ARDUINOJSON_VERSION_MAJOR) && ARDUINOJSON_VERSION_MAJOR >= 6 serializeJson(json, Serial); serializeJson(json, configFile); #else json.printTo(Serial); json.printTo(configFile); #endif configFile.close(); //end save } Serial.println("local ip"); Serial.println(WiFi.localIP()); } void loop() { // put your main code here, to run repeatedly: } ``` ### Debug Messages ``` The values in the file are: 12:13:58.156 -> mqtt_server : google.com 12:13:58.156 -> mqtt_port : 8080 12:13:58.156 -> api_token : 22 12:13:58.156 -> saving config 12:13:58.156 -> failed to open config file for writing 12:13:58.156 -> {"mqtt_server":"google.com","mqtt_port":"8080","api_token":"22"}local ip 12:13:58.156 -> 10.0.1.99```

kerem closed this issue

2026-02-28 01:29:40 +03:00

kerem commented

2026-02-28 01:29:40 +03:00

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Owner

@Gilabo commented on GitHub (Mar 14, 2023):

currently SPIFFS is not compatible with Arduino IDE v2.0

@Gilabo commented on GitHub (Mar 14, 2023): currently SPIFFS is not compatible with Arduino IDE v2.0

kerem commented

2026-02-28 01:29:40 +03:00

Author

Owner

@xpeqex commented on GitHub (Mar 14, 2023):

currently SPIFFS is not compatible with Arduino IDE v2.0

Already tested on v1.8.19 and have the same result :/

@xpeqex commented on GitHub (Mar 14, 2023): > currently SPIFFS is not compatible with Arduino IDE v2.0 Already tested on v1.8.19 and have the same result :/

kerem commented

2026-02-28 01:29:40 +03:00

Author

Owner

@Gilabo commented on GitHub (Mar 15, 2023):

Working fine with me. V1.8.19.
Have you formated FS for SPIFFS first?
I would try with basic SPIFFS example first to see if the library can do read/write a file.
If can, then you might be need to dig into wifimanager settings.

@Gilabo commented on GitHub (Mar 15, 2023): Working fine with me. V1.8.19. Have you formated FS for SPIFFS first? I would try with basic SPIFFS example first to see if the library can do read/write a file. If can, then you might be need to dig into wifimanager settings.

kerem commented

2026-02-28 01:29:40 +03:00

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Owner

@xpeqex commented on GitHub (Mar 16, 2023):

@Gilabo Yeah the solution was to format first then do the rest, sorry I wasn't aware of this.

Anyway, thank you, appreciate it!

@xpeqex commented on GitHub (Mar 16, 2023): @Gilabo Yeah the solution was to format first then do the rest, sorry I wasn't aware of this. Anyway, thank you, appreciate it!

kerem referenced this issue

2026-02-28 02:12:58 +03:00

[PR #1557] added web flasher to repo #1779

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[GH-ISSUE #1572] ESP32-S2 failed to open config file or writing #1339

Description

Settings in IDE

Sketch

Debug Messages