LittleFS filesystem
Overview
This sample app demonstrates use of Zephyr’s 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.
Requirements
Flash memory device
The partition labeled “storage” will be used for the file system; see Flash map. 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.
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 Nucleo H743ZI board. It can be also run on any other board with SD/MMC card connected to it.
To build the test:
west build -b nucleo_h743zi samples/subsys/fs/littlefs -- -DCONF_FILE=prj_blk.conf
west flash
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
CONFIG_SDMMC_VOLUME_NAMEconfiguration is defined, it will be used as the mount point name;if the
CONFIG_SDMMC_VOLUME_NAMEconfiguration is not defined, but theCONFIG_MMC_VOLUME_NAMEconfiguration is defined,CONFIG_MMC_VOLUME_NAMEwill be used as the mount point name;if neither
CONFIG_SDMMC_VOLUME_NAMEnorCONFIG_MMC_VOLUME_NAMEconfigurations 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.
west build -b nrf52840dk/nrf52840 samples/subsys/fs/littlefs
Particle Xenon
On this device the file system will be placed on the external SPI NOR flash memory.
west build -b particle_xenon samples/subsys/fs/littlefs