Help Needed: SPIFFS not showing expected file contents in Serial Monitor (ESP32)

Development Tools IDE 2.x
1

Hi all,

I'm working with an ESP32 and trying to manually upload a SPIFFS filesystem using mkspiffs.exe and esptool.exe. The process seems to complete without errors, but when I try to read the file in my sketch, I don’t get the expected output.

Folder structure:

kotlin

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C:\esp32-spiffs\
├── mkspiffs.exe
├── spiffs.bin
├── GOTID_SPIFFS_Test\
│   ├── data\
│   │   └── example.txt

Contents of example.txt:

kotlin

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This is a test file inside SPIFFS.
If you can see this, your SPIFFS works!

Command to create spiffs.bin:

css

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mkspiffs.exe -c GOTID_SPIFFS_Test\data -b 4096 -p 256 -s 0x110000 spiffs.bin

Command to flash it:

css

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esptool.exe --chip esp32 --port COM5 --baud 921600 write_flash 0x110000 ..\..\spiffs.bin

Both commands complete successfully. spiffs.bin is created and flashes to the ESP32 without error. I verified the COM port and board settings (ESP32 Dev Module on COM5). Uploads via Arduino IDE also work fine.

Test sketch:

cpp

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#include "FS.h"
#include "SPIFFS.h"

void setup() {
  Serial.begin(115200);
  delay(1000);

  if (!SPIFFS.begin(true)) {
    Serial.println("SPIFFS Mount Failed");
    return;
  }

  File file = SPIFFS.open("/example.txt");
  if (!file) {
    Serial.println("Failed to open file for reading");
    return;
  }

  Serial.println("File Content:");
  while (file.available()) {
    Serial.write(file.read());
  }
  file.close();
}

void loop() {}

Problem:

When I open the Serial Monitor, instead of seeing the content of example.txt, I either get:

yaml

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File Content:
ets Jul 29 2019 12:21:46

or just nothing at all. Sometimes only the “File Content:” line appears with no actual text after it.

What I’ve confirmed:

  • The file is saved as plain text
  • I’ve regenerated and reflashed spiffs.bin multiple times
  • Flashing shows success (hash verified, hard resetting via RTS)
  • The same sketch has worked for other SPIFFS setups when using Arduino’s built-in SPIFFS upload tool

What am I missing here? Is something going wrong during the SPIFFS image creation or flashing, even though no errors are reported?

Appreciate any help from the community. Thanks.

2

All those kotlin and talk scattered in your text seems to indicate a copy and paste from ChatGPT or similar AI… are you working with AI?

Any reason why you don’t use the data upload tool that you can install in the IDE?

1 Like
3

Are you aware that SPIFFS is deprecated? I think LittleFS is the 'new' SPIFFS.

4

Thanks for the info. I’ve decided to go back to Arduino IDE 1.8.x since it fully supports the ESP32 SPIFFS Upload Tool. I now understand that the newer 2.x IDE doesn’t support the plugin, which explains a lot of the issues I ran into. I’ll continue working with 1.8.x for now as it’s more stable for SPIFFS uploads.

Appreciate the guidance.

5

Hi @me109bf.

It is true that Arduino IDE 2.x does not support the plugins that were created for the Arduino IDE 1.x "Tools" framework. However, there is a high quality and very well maintained replacement extension for Arduino IDE 2.x you can use to upload littlefs filesystems to the ESP32 board: