3. Filesystems and Storage¶
Storage modules support virtual filesystem with FAT and littlefs formats, backed by either Zephyr DiskAccess or FlashArea (flash map) APIs depending on which the board supports.
3.1. Disk Access¶
For use with SD card controllers, SD cards must be present at boot & not removed; they will be auto detected and initialized by filesystem at boot. Use the disk driver interface and a file system to access SD cards via disk access (see below).
Example usage of FatFS with an SD card on the mimxrt1050_evk board:
import os from zephyr import DiskAccess bdev = zephyr.DiskAccess('SDHC') # create block device object using DiskAccess os.VfsFat.mkfs(bdev) # create FAT filesystem object using the disk storage block os.mount(bdev, '/sd') # mount the filesystem at the SD card subdirectory with open('/sd/hello.txt','w') as f: # open a new file in the directory f.write('Hello world') # write to the file print(open('/sd/hello.txt').read()) # print contents of the file
3.2. Flash Area¶
The zephyr.FlashArea class can be used to implement a low-level storage system or customize filesystem configurations. To store persistent data on the device, using a higher-level filesystem API is recommended (see below).
Example usage with the internal flash on the reel_board or the rv32m1_vega_ri5cy board:
import os from zephyr import FlashArea bdev = FlashArea(FlashArea.STORAGE, 4096) # create block device object using FlashArea os.VfsLfs2.mkfs(bdev) # create Little filesystem object using the flash area block os.mount(bdev, '/flash') # mount the filesystem at the flash storage subdirectory with open('/flash/hello.txt','w') as f: # open a new file in the directory f.write('Hello world') # write to the file print(open('/flash/hello.txt').read()) # print contents of the file
For boards such as the frdm_k64f in which the MicroPython application spills into the default flash storage
partition, use the scratch partition by replacing
FlashArea.STORAGE with the integer value 4.