FatFs

FatFs is a lightweight software library for microcontrollers and embedded systems that implements FAT/exFAT file system support.[1] Written on pure ANSI C, FatFs is platform-independent and easy to port on many hardware platforms such as 8051, PIC, AVR, ARM, Z80. FatFs is designed as thread-safe and is built into ChibiOS, RT-Thread, and Zephyr real-time operating systems.[2]

FatFs
Developer(s)ChaN
Initial releaseFebruary 26, 2006 (2006-02-26)
Stable release
R0.15 / 2022
RepositoryReleases archive
Written inANSI C
PlatformIntel 8051, PIC, AVR, ARM, Z80
TypeEmbedded systems software
LicenseOwn license, similar to BSD
Websiteelm-chan.org

Most often, FatFs is used in low-power Embedded systems where memory is limited, since the library takes up little space in RAM and program code. In the minimum version, the working code takes from 2 to 10 kB of RAM.[3]

Overview

FatFs is designed to be a Filesystem Layer that is agnostic to the platform and storage media it is used with. This is achieved by providing a media access interface that is used to communicate with the storage device control module which is provided by the implementer.[4] This means that FatFs can work with any physical device such as an SD card or a hard disk on any platform that can run plain C code if the implementer provides a control module interface.

Architecture
FatFs Architecture layers scheme

FatFs library architecture logically separates the abstractions of the user app and the platform-dependent code. The user application and the low level disk I/O layer (driver) must be added by the implementer.[4]: 11  Also, the architecture of the library implies that the system can have several storage devices with different drivers and the library can work in a multi-threaded operating system. At the application level it is hidden which physical media is used.

In the minimum implementation, the driver layer must support at least these 3 interfaces:[4]: 14 

  • disk_status — return block device status (not initialized, missing, protected, ready)
  • disk_initialize — initialize the physical disk
  • disk_read — read block from physical disk

This level of abstraction allows implementers to write an application once, and then port it on different platforms, changing only the implementation of the driver.[5]

License

FatFs has its own minimalistic license [6] similar to the BSD license. It allows usage in commercial products without disclosing the source code.[4]: 12  The only condition is to keep the copyright notice in case of redistribution of the source code. The conditions of FatFs license are not cover any redistributions in binary form, such as embedded code and hex files.

Projects using FatFs

References
  1. Ivan Cibrario Bertolotti (2016). Embedded Software Development; The Open-Source Approach. Tingting Hu. p. 361. ISBN 9781466593930. OCLC 932464067.
  2. Yi Qiu (2020). The design and implementation of the RT-thread operating system. Xiong Puxiang, Tianlong Zhu. p. 361. ISBN 9780367554866. OCLC 1197810565.
  3. "FatFs Memory Usage comparison table". elm-chan.org. Retrieved 2022-06-17.
  4. "Developing applications on STM32Cube with FatFs" (PDF). STMicroelectronics. Retrieved 22 June 2022.
  5. Beningo, Jacob (2017). Reusable Firmware Development; A Practical Approach to APIs, HALs and Drivers. p. 255. ISBN 9781484232972. OCLC 1484232976.
  6. "FatFs License". elm-chan.org. Retrieved 2022-06-17.
  7. "FatFs Library description on Arduino platform documentation". Arduino Official Website. Retrieved 2022-06-17.
  8. "FAT Filesystem Support - ESP32 - — ESP-IDF Programming Guide latest documentation". docs.espressif.com. Retrieved 2022-06-27.
  9. "FatFs File System Configuration in rt-thread operating system". www.rt-thread.io. Retrieved 2022-06-26.
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