.. zephyr:code-sample:: littlefs
:name: LittleFS filesystem
:relevant-api: file_system_api flash_area_api
Use file system API over LittleFS.
Overview
********
This sample app demonstrates use of Zephyr's :ref:`file system API
<file_system_api>` over `littlefs`_, using file system with files that:
* count the number of times the system has booted
* holds binary pattern with properly incremented values in it
Other information about the file system is also displayed.
.. _littlefs:
https://github.com/ARMmbed/littlefs
Requirements
************
Flash memory device
-------------------
The partition labeled "storage" will be used for the file system; see
:ref:`flash_map_api`. If that area does not already have a
compatible littlefs file system its contents will be replaced by an
empty file system. You will see diagnostics like this::
[00:00:00.010,192] <inf> littlefs: LittleFS version 2.0, disk version 2.0
[00:00:00.010,559] <err> littlefs: Corrupted dir pair at 0 1
[00:00:00.010,559] <wrn> littlefs: can't mount (LFS -84); formatting
The error and warning are normal for a new file system.
After the file system is mounted you'll also see::
[00:00:00.182,434] <inf> littlefs: filesystem mounted!
[00:00:00.867,034] <err> fs: failed get file or dir stat (-2)
This error is also normal for Zephyr not finding a file (the boot count,
in this case).
Block device (e.g. SD card)
---------------------------
One needs to prepare the SD/MMC card with littlefs file system on
the host machine with the `lfs`_ program.
.. _lfs:
https://www.thevtool.com/mounting-littlefs-on-linux-machine/
.. code-block:: console
sudo chmod a+rw /dev/sda
lfs -d -s -f --read_size=512 --prog_size=512 --block_size=512 --cache_size=512 --lookahead_size=8192 --format /dev/sda
lfs -d -s -f --read_size=512 --prog_size=512 --block_size=512 --cache_size=512 --lookahead_size=8192 /dev/sda ./mnt_littlefs
cd ./mnt_littlefs
echo -en '\x01' > foo.txt
cd -
fusermount -u ./mnt_littlefs
Building and Running
********************
Flash memory device
-------------------
This example should work on any board that provides a "storage"
partition. Two tested board targets are described below.
You can set ``CONFIG_APP_WIPE_STORAGE`` to force the file system to be
recreated.
Block device (e.g. SD card)
---------------------------
This example has been devised and initially tested on :ref:`Nucleo H743ZI <nucleo_h743zi_board>`
board. It can be also run on any other board with SD/MMC card connected to it.
To build the test:
.. zephyr-app-commands::
:zephyr-app: samples/subsys/fs/littlefs
:board: nucleo_h743zi
:goals: build flash
:gen-args: -DCONF_FILE=prj_blk.conf
:compact:
At the moment, only two types of block devices are acceptable in this sample: SDMMC and MMC.
It is possible that both the ``zephyr,sdmmc-disk`` and ``zephyr,mmc-disk`` block devices will be
present and enabled in the final board dts and configuration files simultaneously, the mount
point name for the ``littlefs`` file system block device will be determined based on the
following logic:
* if the :kconfig:option:`CONFIG_SDMMC_VOLUME_NAME` configuration is defined, it will be used
as the mount point name;
* if the :kconfig:option:`CONFIG_SDMMC_VOLUME_NAME` configuration is not defined, but the
:kconfig:option:`CONFIG_MMC_VOLUME_NAME` configuration is defined,
:kconfig:option:`CONFIG_MMC_VOLUME_NAME` will be used as the mount point name;
* if neither :kconfig:option:`CONFIG_SDMMC_VOLUME_NAME` nor :kconfig:option:`CONFIG_MMC_VOLUME_NAME`
configurations are defined, the mount point name will not be determined, and an appropriate error
will appear during the sample build.
NRF52840 Development Kit
========================
On this device the file system will be placed in the SOC flash.
.. zephyr-app-commands::
:zephyr-app: samples/subsys/fs/littlefs
:board: nrf52840dk/nrf52840
:goals: build
:compact:
Particle Xenon
==============
On this device the file system will be placed on the external SPI NOR
flash memory.
.. zephyr-app-commands::
:zephyr-app: samples/subsys/fs/littlefs
:board: particle_xenon
:goals: build
:compact:
cb47c62259