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134 lines
6.0 KiB
ReStructuredText
134 lines
6.0 KiB
ReStructuredText
SPIFFS Filesystem
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=================
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Overview
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--------
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SPIFFS is a file system intended for SPI NOR flash devices on embedded targets.
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It supports wear leveling, file system consistency checks and more.
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Notes
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-----
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- Currently, SPIFFS does not support directories. It produces a flat structure. If SPIFFS is mounted under ``/spiffs``, then creating a file with path ``/spiffs/tmp/myfile.txt`` will create a file called ``/tmp/myfile.txt`` in SPIFFS, instead of ``myfile.txt`` under directory ``/spiffs/tmp``.
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- It is not a realtime stack. One write operation might last much longer than another.
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- Currently, it does not detect or handle bad blocks.
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Tools
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-----
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spiffsgen.py
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^^^^^^^^^^^^
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:component_file:`spiffsgen.py<spiffs/spiffsgen.py>` is a write-only Python SPIFFS implementation used to create filesystem
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images from the contents of a host folder. To use ``spiffsgen.py``, simply invoke it from your favorite terminal::
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python spiffsgen.py <image_size> <base_dir> <output_file>
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- image_size: size of the partition on which the created SPIFFS image will be flashed to
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- base_dir: directory to create the SPIFFS image of
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- output_file: SPIFFS image output file
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Besides the three required arguments: *image_size*, *base_dir* and *output_file*, there are other arguments
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that control image generation. Documentation on these arguments exist in the tool's help::
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python spiffsgen.py --help
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These optional arguments correspond to possible SPIFFS build configuration.
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User should make sure that the image is generated with the same arguments/configuration as
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SPIFFS was built with, else the user ends up with an invalid image. As a guide, the help output indicates the SPIFFS
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build configuration the argument corresponds to. In cases when these arguments
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are not specified, the default values shown in the help output are used.
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Once the image has been created, it can be flashed using ``esptool.py`` or ``parttool.py``.
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Aside from invoking ``spiffsgen.py`` standalone, it is also possible to use it directly from the build system by calling
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``spiffs_create_partition_image``.
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Make::
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$(eval $(call spiffs_create_partition_image,<partition>,<base_dir>,[FLASH_IN_PROJECT]))
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CMake::
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spiffs_create_partition_image(<partition> <base_dir> [FLASH_IN_PROJECT])
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This is more convenient as the build configuration is automatically passed to the tool,
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ensuring that the image generated is valid for that build. An example of this is while the *image_size* is required
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for the standalone invocation, only the *partition* name is required when using ``spiffs_create_partition_image`` --
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the image size is automatically obtained from the project's partition table.
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It is important to note that due to the differences in structure between the two build systems,
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when using Make, ``spiffs_create_partition_image`` must be called from the project Makefile;
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for CMake, it should be called from one of the component CMakeLists.txt. For both build systems, the image will be created in the build directory
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with filename *partition*.bin.
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Optionally, user can opt to have the image automatically flashed together with the app binaries, partition tables, etc. on
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``idf.py flash`` or ``make flash`` by specifying ``FLASH_IN_PROJECT``. For example::
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spiffs_create_partition_image(my_spiffs_partition my_folder FLASH_IN_PROJECT)
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If FLASH_IN_PROJECT is not specified, the image is still generated,
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but user has to flash it manually using ``esptool.py``, ``parttool.py`` or a custom build system target.
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For an example, see :example:`examples/storage/spiffsgen>`.
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mkspiffs
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^^^^^^^^
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Another tool for creating SPIFS partition images is `mkspiffs <https://github.com/igrr/mkspiffs>`_.
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Like ``spiffsgen.py``, it can be used to create image from a given folder and then flash that image with ``esptool.py``
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To do that you need to obtain some parameters:
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- Block Size: 4096 (standard for SPI Flash)
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- Page Size: 256 (standard for SPI Flash)
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- Image Size: Size of the partition in bytes (can be obtained from partition table)
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- Partition Offset: Starting address of the partition (can be obtained from partition table)
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To pack a folder into 1 Megabyte image::
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mkspiffs -c [src_folder] -b 4096 -p 256 -s 0x100000 spiffs.bin
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To flash the image to ESP32 at offset 0x110000::
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python esptool.py --chip esp32 --port [port] --baud [baud] write_flash -z 0x110000 spiffs.bin
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Notes on which SPIFFS tool to use
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The two tools presented above offer very similar functionality. There are, however, reasons to prefer one
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over the other depending on the use case.
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If the intent is to simply generate a SPIFFS image during build, ``spiffsgen.py`` makes it very convenient
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by providing functions/commands from the build system itself. This makes it easy to generate SPIFFS images
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that match the build configuration and can be flashed together with the application.
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Another case for choosing ``spiffsgen.py`` is when the host has no C/C++ compiler available, since ``mkspiffs``
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requires compilation.
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On the other hand, ``mkspiffs`` offers unpacking SPIFFS images in addition to image generation. This is not
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possible with ``spiffsgen.py``, at least not yet. There might also be environments where a Python interpreter
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is not available, but a host compiler is or a pre-compiled ``mkspiffs`` binary
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can do the job. However, there is no build system integration for ``mkspiffs`` and the user has to
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do the corresponding work: compiling ``mkspiffs`` during build (if a pre-compiled binary is not used), creating build rules/targets
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for the output files, passing proper parameters to the tool, etc.
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See also
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--------
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- :doc:`Partition Table documentation <../../api-guides/partition-tables>`
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Application Example
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-------------------
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An example for using SPIFFS is provided in :example:`storage/spiffs` directory. This example initializes and mounts SPIFFS partition, and writes and reads data from it using POSIX and C library APIs. See README.md file in the example directory for more information.
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High level API Reference
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------------------------
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* :component_file:`spiffs/include/esp_spiffs.h`
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.. include:: /_build/inc/esp_spiffs.inc
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