External flash for ESP32-C3-MINI-1

[nogema]

Hello,

I would like to add an external flash to increase the amount of data that I can treat with the RAM. I am using a custom board with the ESP32-C3-MINI-1 chip and a SST25VF080B SPI flash.
I tried to run the ext flash fats example of ESP-IDF but it fails : I succed to add the external partition and to mount the FAT filesystem (with a warning because it fails once) but when I read the partition information with esp_vfs_fat_info(), I get

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E (372) vfs_fat: Failed to get number of free clusters (13)

And when I try to create a file with fopen(), I get

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E (382) example: Failed to open file for writing

I have already checked all the pins and try to change the base path. The example wear levelling works well.
One thing to note : I have to specify the size of the external flash otherwise it allocates 16 kB instead of 1 MB.

Does anyone have an idea what is wrong ? Or maybe it is impossible to add an external flash to the ESP32-C3-MINI-1 ?

Thank you in advance

Regards,