UTFS is a lightweight, zero-allocation file system for embedded devices

CLI Systems has introduced UTFS (μTFS), a simple, lightweight embedded storage system designed for small MCUs. Unlike traditional file systems like FAT32 or EXT4, or even lighter options like LittleFS and SPIFFS used on boards like the ESP32, UTFS is much simpler. It does not use dynamic memory and avoids complex features like wear leveling, making it easier to use on low-resource devices.

Designed for flat, byte-addressable memory like raw EEPROM, CPU flash pages, or external SPI/I²C flash, UTFS allows bare-metal firmware to store named data blobs (“files”) back-to-back. Each file is appended with a fixed 24-byte header containing metadata like identifiers, sizes, and application-defined signatures.

UTFS specifications and features

• Footprint – Fixed 24-byte header per file; zero heap usage (no malloc)
• Format – TAR-inspired sequential layout; forward-compatible so files can be added later without breaking existing memory layouts
• Storage Agnostic – Requires porting only two functions to interface with the hardware medium: sys_read and sys_write
• Reliability – Uses application-defined signatures (e.g., 0xABCD) to detect corrupt or uninitialized storage upon the initial utfs_load() call
• License – Open-source under the MIT License, completely unencumbered by proprietary vendor formats

Many microcontroller projects just store all data as one large structure at a fixed EEPROM address. This is simple, but it becomes a problem if the data format changes later, since older data may no longer work. On the other hand, full file systems like FatFs or LittleFS offer advanced features but require more memory and are heavier to run on small devices.

UTFS sits between these two approaches. It doesn’t include advanced features like wear leveling or safe atomic writes, so if power is lost during a save, data can be partially written, just like with normal EEPROM writes. Instead, it keeps things simple by storing data as separate named blocks, making it easier to manage and update data on small systems that don’t have enough resources for a full file system.

More information, including working examples for boards like the Arduino Uno (ATmega328), which uses built-in EEPROM, and the Microchip SAMD20, which uses internal flash memory, can be found on the CLI Systems page. To use UTFS on other hardware, you only need to connect its API to the device’s read and write functions. The C99 source code, examples, and full documentation are available on the CLI Systems GitHub repository for integration into projects.

Via Hackaday

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