Storage API

[中文]

This section contains reference of the high-level storage APIs. They are based on low-level drivers such as SPI flash, SD/MMC.

• Partitions API allow block based access to SPI flash according to the Partition Tables.

• Non-Volatile Storage library (NVS) implements a fault-tolerant wear-levelled key-value storage in SPI NOR flash.

• Virtual File System (VFS) library provides an interface for registration of file system drivers. SPIFFS, FAT and various other file system libraries are based on the VFS.

• SPIFFS is a wear-levelled file system optimized for SPI NOR flash, well suited for small partition sizes and low throughput

• FAT is a standard file system which can be used in SPI flash or on SD/MMC cards

• Wear Levelling library implements a flash translation layer (FTL) suitable for SPI NOR flash. It is used as a container for FAT partitions in flash.

Topics related to Storage Security are described in separate section.

Note

It is suggested to use high-level APIs (esp_partition or file system) instead of low-level driver APIs to access the SPI NOR flash.

Due to the restriction of NOR flash and ESP hardware, accessing the main flash will affect the performance of the whole system. See SPI Flash API to learn more about the limitations.

• FAT Filesystem Support
• Generating and Parsing FATFS on Host
• Manufacturing Utility
• Non-Volatile Storage Library
• NVS Encryption
• NVS Partition Generator Utility
• NVS Partition Parser Utility
• SD/SDIO/MMC Driver
• Partitions API
• SPIFFS Filesystem
• Virtual Filesystem Component
• Wear Levelling API
• Storage Security

Code examples for this API section

Link	Description
FAT
<wear_levelling	Demonstrates using FATFS over wear leveling on internal flash.
ext_flash_fatfs	Demonstrates using FATFS over wear leveling on external flash.
fatfsgen	Demonstrates the capabilities of Python-based tooling for FATFS images available on host computers.
Non-Volatile Storage library (NVS)
nvs_rw_blob	Shows the use of the C-style API to read and write blob data types in NVS flash.
nvs_rw_value	Shows the use of the C-style API to read and write integer data types in NVS flash.
nvs_rw_value_cxx	Shows the use of the C++-style API to read and write integer data types in NVS flash.
nvsgen	Demonstrates how to use the Python-based NVS image generation tool to create an NVS partition image from the contents of a CSV file.
SPIFFS
spiffs	Shows the use of the SPIFFS API to initialize the filesystem and work with files using POSIX functions.
spiffsgen	Demonstrates the capabilities of Python-based tooling for SPIFFS images available on host computers.
Partitions API
partition_api	Provides an overview of API functions to look up particular partitions, perform basic I/O operations, and use partitions via CPU memory mapping.
parttool	Demonstrates the capabilities of Python-based tooling for partition images available on host computers.
Virtual File System (VFS)
littlefs	Shows the use of the LittleFS component to initialize the filesystem and work with a file using POSIX functions.
semihost_vfs	Demonstrates the use of the VFS API to let an ESP-based device access a file on a JTAG-connected host using POSIX functions.

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