Little File System (LittleFS) Architecture#

The Little File System (LittleFS) is a lightweight, fault-tolerant file system optimized for embedded systems with limited flash memory and processing resources. It provides data reliability, wear leveling, and power-loss recovery, making it a robust choice for persistent storage on SiWx917 and similar devices.

High-Level Diagram#

The following diagram shows the LittleFS architecture and its interaction with the underlying flash storage.

LittleFS Architecture DiagramLittleFS Architecture Diagram

Overview#

LittleFS is designed to make the most efficient use of flash storage while maintaining high reliability.
Its architecture addresses key flash-specific challenges such as limited write endurance, power-failure safety, and bad-block management—all within a small memory footprint.

Key Capabilities#

  • Reliable storage with atomic updates

  • Fault tolerance and recovery after unexpected resets or power failures

  • Dynamic wear leveling to extend flash lifetime

  • Low RAM and ROM footprint suitable for constrained microcontrollers (MCUs)

General Concepts#

  • Power-loss resilience:

    • Uses copy-on-write (COW) and rollback mechanisms to guarantee data integrity.

    • After a sudden power loss, the system automatically recovers to the last stable state.

  • Wear leveling

    • Distributes write and erase cycles evenly across flash memory blocks.

    • Prevents premature wear-out of specific regions, ensuring long-term durability.

  • Small footprint

    • Optimized for minimal RAM and ROM use.

    • Ideal for microcontrollers with limited flash capacity (as low as 64 KB).

  • Block-based design

    • Divides the flash storage into fixed-size blocks, which are the primary data management units.

    • Simplifies memory mapping and improves access consistency.

  • Copy-on-write (COW)

    • When modifying data, LittleFS writes updates to a new block instead of overwriting the existing one.

    • Guarantees atomic operations and eliminates the risk of partial data corruption.

  • Bad-block detection

    • Continuously scans for defective flash blocks.

    • Automatically marks bad blocks as unusable and remaps data accordingly.

Note: LittleFS is an open-source, third-party file system actively maintained by the community.

For in-depth technical information, visit the LittleFS GitHub repository.

Core Components#

The LittleFS stack consists of key components that work together to manage file operations, memory access, and system consistency.

  • Block-Based Storage

    • Manages data allocation and organization within logical blocks.

    • Each block serves as a base unit for reading, writing, and erasing data.

    • Abstracts flash memory details to ensure portability across different hardware.

  • Configuration Structure

    • Defines essential parameters for operation, including:

      • Block read/write functions

      • Block and page sizes

      • Cache and lookahead buffer settings

    • Typically initialized using the lfs_config structure.

  • State Structure (lfs_t)

    • Represents the runtime state of the file system.

    • Developers must allocate and manage this structure to mount and operate multiple LittleFS instances within the same project.

You can add LittleFS to a project through software components (.slcp). For details, see the UC Configuration section.

Directory Structure#

The following directory structure shows how LittleFS integrates into the development environment:

wiseconnect/
├── examples/
│   └── si91x_soc/
│       └── service/
│           └── sl_si91x_littlefs_common_flash
├── third_party/
│   └── littlefs/
│       ├── inc/
│       │   └── lfs.h
│       └── src/     
│           └── lfs.c

Dependencies#

LittleFS depends on several software and hardware components to function correctly in embedded projects:

  • WiSeConnect Software Development Kit (SDK): Must be installed and configured in Simplicity Studio.

  • Simplicity Studio Configuration: Provides integration and management of project components.

  • Universal Configurator (UC): Used to set operational parameters for LittleFS.

  • Clock Source and Divider Settings: Managed through the microcontroller (MCU) clock architecture for Quad Serial Peripheral Interface (QSPI).

  • QSPI Controller: Provides high-speed communication with external flash memory.

  • Non-Volatile Memory (Flash): Serves as the underlying storage medium for the file system.