Fat32 file system corruption on internal flash of ESP32S3

[Kowshik_Bevara]

I am using an [ESP32-S3](https://www.espressif.com/sites/default ... eet_en.pdf) chip with 8 MB internal flash. Out of which 4 MB is for the FAT32 file system. I read and write files every 30 min into the file system. I am also using the wear leveling library that is available in the default ESP32-S3 libraries.

Wear leveling is to prolong their lifespan and improve performance. Flash memory has a limited number of write and erase cycles before individual memory cells can no longer reliably store data. Wear leveling helps distribute these write-and-erase cycles evenly across the memory cells, preventing some cells from wearing out prematurely while others remain unused.

Now, In some rare cases even though the file system is not having many files, the 4 MB is getting full. I even ran Defragger to check if there was any fragmentation issue, but it says there are 0 fragments.

Now I don't know what exactly is occupying the space here and how to check it.

Please note: we are using 1000's of devices with the same code, and the issue is piling up only in 10-15 devices and these devices used to work fine previously for months.

Below is the partition table I'm using. I'm not using any extended storage.

|# Name, | Type, |SubType, | Offset, | Size, |
|:-------------|:------|:----------|:---------|:--------|
| nvs, | 0x01, | nvs, |0x11000, |0x8000, |
|otadata, | 0x01, |ota, |0x19000, |0x2000, |
|phy_init, | 0x01, |phy, |0x21000, |0x3000, |
|ota_0, | 0x00, |ota_0, |0x110000, |0x140000,|
|ota_1, | 0x00, |ota_1, |0x250000, |0x140000,|
|fatfs_storage,| 0x01, |fat, |, |4M, |

I have looked at the volume ID sector. I have used analyzer tools on it, it shows that the files occupy the expected space inside the volume but it does not show what data is filling the rest of the memory.

Let me know if any more information is required.

Below is the code for the FAT32 file system initialization

bool FatFS_initialize(bool make_fs)
{
FRESULT fr_result;
BYTE pdrv;
FATFS *fs;

esp_err_t esp_result;

static bool first_call = true; // just to make sure FS registration isn't done even if this function is called another time
if (first_call)
{
const esp_partition_t *partition = esp_partition_find_first(ESP_PARTITION_TYPE_DATA, ESP_PARTITION_SUBTYPE_DATA_FAT, "fatfs_storage");
if (partition == NULL)
{
ESP_LOGE("FatFS", "Failed to find FATFS partition (type='data', subtype='fat', partition_label='%s'). Check the partition table.", "fatfs_storage");
return false;
}
esp_err_t ret = esp_vfs_fat_register(fatfs_base_path, "", 5, &fs);
if (ret != ESP_OK)
{
ESP_LOGE("FatFS", "VFS registration error(%u)", ret);
return false;
}

wl_handle_t wl_handle;
esp_result = wl_mount(partition, &wl_handle);
if (esp_result != ESP_OK)
ESP_LOGE("FatFS", "wl_mount error");

// Get a physical drive
esp_result = ff_diskio_get_drive(&pdrv);
if (esp_result != ESP_OK)
ESP_LOGE("FatFS", "get drive error");

// Register physical drive as wear-levelled partition
esp_result = ff_diskio_register_wl_partition(pdrv, wl_handle);
if (esp_result != ESP_OK)
ESP_LOGE("FatFS", "disk register error");

if (make_fs)
{
BYTE work_area[FF_MAX_SS];
fr_result = f_mkfs("", FS_FAT32, 0, work_area, FF_MAX_SS); // Use default volume
if (fr_result != FR_OK)
{
ESP_LOGE("FatFS", "f_mkfs error : %d", fr_result);
return false;
}
else
{
ESP_LOGI("FatFS", "File system created successfully");
}
}

first_call = false;
}
return true;
}

[pacucha42]

Hi Kowshik_Bevara,
thank you for the report. Sorry to hear you are having troubles with your project. Please, consider using high-level APIs for mounting: https://docs.espressif.com/projects/esp ... l_handle_t for mounting (includes formatting too) and https://docs.espressif.com/projects/esp ... l_handle_t for unmounting.

Doing all the internal steps manually is tricky and not recommended unless you have a strong reason to do so.

NOTE: Wear-Levelling has minor performance impact, thus not really improving the speed/throughput. The only goal is to prolong the lifetime of SPI Flash media, as you have correctly mentioned.

If your troubles persist after switching to the recommended APIs, let me know, please