ESP32 and SD Card ?

[espruino-discuss3]

Posted at 2024-11-19 by JumJum

In a project some data should be stored for later use.
My decision is to use an SD Card, to be open for a lot of data.
Problem is E.connectSDCard, I get an error message.
Somewhere in my mind is a feedback like "you have to build your own binary"
After some jumping through sources, I could see FLASHFS and FILESYSTEM.
This is where some confusions starts with different boardfiles for ESP32
First is ESP32.py having both set
Next is ESP32_IDF4.py where both are commented
And for different boards
ESP32C3_IDF4.py, both are commented
ESP32S3_IDF4.py, only FLASHFS is commented

What is the reason for different handling.
What should I do to build a version which supports SD Cards and runs on a standard ESP32 ?
I could use ESP32 WROVER oder WROOM and would prefer the WROVER with additional memory

[espruino-discuss3]

Posted at 2024-11-20 by @gfwilliams

I think you need FILESYSTEM but not FLASHFS.

FLASHFS was added in espruino/Espruino@a167bd3
to allow some of the flash memory to be used by turning it into a FatFS filesystem.

At the time the Storage module didn't handle multiple files well so @wilberforce wanted wanted a way to expose it, but I believe doing so uses FatFS so it can't be used for other stuff (at least in the current implementation).

Personally I'd like to remove FLASHFS totally now. I don't know what others think but IMO it's a bit confusing having two different filesystems, one of which appears in the IDE one of which doesn't. For instance the second post on the forum right now is https://forum.espruino.com/conversations/400842/#comment17584054 where this exact thing has happened

We could remove FlashFS and change the partitions so we have a great big area for Storage - and because of the way Storage stores data it's all memory-mapped, so if you write something to it (for example an image) it can be used in Espruino straight from Flash without ever loading it into RAM.

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Posted at 2024-11-21 by JumJum

Flashfs needs to be disabled to have E.connectSDCard running (see jswrap_file.c)
Comparing the comfort of having a file system for flash memory (storage), and not having the chance to use an SD Card, my winner is SD Card.
Last not least looks to me Flashfs being a special function for ESP32 only.

[SimonGAndrews]

@gfwilliams Is this the background to the commit on April 1 or 2, 2025 'ESP32: Remove FlashFS, adjust partitions to increase available Storage from 256kB to 896kB'.

[gfwilliams]

Yes - that and https://github.com/orgs/espruino/discussions/7488 where people were wondering why they only got 250k storage on a 4MB chip :) The IDE makes reading/writing files to Storage reasonably painless, but it was pretty difficult writing to the FAT filesystem on the ESP32 which made its use pretty minimal

... not to mention on the C3/S3 ports we weren't using FlashFS but still had the partitions so that 640k was just sitting there unused

So now you should be able to use external SD cards just fine I hope.