JesFs - Jo's Embedded Serial File System V2.02

for Standard (Serial) NOR-Flash

Just think of very simple things like language data: on a “very small” Embedded Device (not something “big” like an Embedded Linux, but something that can run with small batteries for years): it is commonly integrated “somewhere in the code”.
Difficult to change! But if the language data is in files, changes are easy. Same for graphics, setups, everything… It even allows to change the firmware on the Embedded Device from many different sources!

Think of Embedded Devices, that even can get their latest firmware by themselves! E.g. over WiFi, Mobile Internet, Bluetooth, UART, Radio-Link, …
Suddenly all options are open! And if you have concerns about the security: don’t worry: problem already solved, as you’ll see later..

The main problem for “very small devices” – until now – was the “File System”: everybody knows “FAT”, “NTFS”, … but have you ever thought of a file system on a small chip? Or even inside of a CPU? No problem, with the right Software. This is why I wrote

“JesFs – Jo’s Embedded Serial File System“

JesFs on LTraX

[Image: JesFs on the LTraX module (CC1310)]

JesFs on RC-CC1310F

[Image: offers a very compact CC1310F module with 2MB Flash]

My daily work ist the IoT. Because I did not find any really practical solution, I decided to create my own one. “Robustness”, “Security” and “Small Footprint” were my design constraints.

JesFs was designed for use in the “Real World” and for use with standard Serial NOR-Flash memories, like the M25R-Series, used on nRF52840-DK and the CC13xx/CC26xx Launchpads, which is available up to 16 MB, or even more…

Some Basics about JesFs:

  • Ultra-Small RAM and code footprint: can be used on the smallest MCUs with only 8kByte program memory or less (like the famous MSP430-series, almost all kind of 32-Bit ARM cores (M0, M3, M4, ….)). Only 200 Bytes of RAM are sufficient!
  • Completely Open Source (GPL v3) and written in Standard C.
  • Works with Serial NOR-Flash from 8kByte to 16MByte (opt. up to 2GByte), but could also be used with CPU-internal NOR-Flash.
  • Works hand-in-hand with the Ultra-Small JesFsBoot Secure bootloader (requires less than 8kB on standard ARM cores, including an AES-128 encryption engine for reliable Over-the-Air-Updates (“OTA”)).
  • Includes optimised Wear Leveling (for maximum life of the memory).
  • Very Fast Data transfer (e.g. reading files: 3.7MB/sec on nRF52840).
  • A special mode was added to allow millions of write cycles, especially for data collection, event reports and journaling aplications.
  • JesFs is persistent: no data loss on Power Loss or Reset.
  • Designed for (almost) all situations, where NOR memories could be used (the ones where only blocks can be deleted (0->1) and only 0 written.
  • Strictly taylored to Ultra-Low-Power Embedded Systems
  • Designed to use the advantage of an underlying RTOS, but can also be used standalone.
  • Sample applications for the nRF52840-DK, Launchpads CC13xx/26xx, Windows-PC and others (Documentation PDF: JesFs.pdf)
  • Easy to use with an intuitive API:
  int16_t fs_open(FS_DESC *pdesc, char* pname, uint8_t flags);
  int32_t fs_read(FS_DESC *pdesc, uint8_t *pdest, uint32_t anz);
  int16_t fs_write(FS_DESC *pdesc, uint8_t *pdata, uint32_t len);
  int16_t fs_close(FS_DESC *pdesc);
  int16_t fs_delete(FS_DESC *pdesc);
  int16_t fs_rewind(FS_DESC *pdesc);
  int16_t fs_rename(FS_DESC *pd_odesc, FS_DESC *pd_ndesc);
  uint32_t fs_get_crc32(FS_DESC *pdesc);
  int16_t fs_check_disk(void cb_printf(char *fmt, ...), uint8_t *pline, uint32_t line_size);

  int16_t fs_format(uint32_t f_id);
  int16_t fs_start(uint8_t mode);
  void fs_deepsleep(void);

  int16_t fs_info(FS_STAT *pstat, uint16_t fno);
  void fs_sec1970_to_date(uint32_t asecs, FS_DATE *pd);


  • V1.0 CC13XX/CC26xx and Windows
  • V1.5 (nRf52) nRF52840 port
  • V1.51 (nRf52) nRF52840 support Deep Sleep/Wakeup (Deep Sleep with RTC active and Full RAM retention <3uA)
  • V1.6 Added 'fs_disk_check()': careful Disk Check
  • V1.61 (nRf52) source cosmetics and reduced default SPIM Clock to 16MHz on nRF52840 (32MHz recommended only without Softdevice)
  • V1.7 (nRf52) Added Defines for u-Blox NINA-B3
  • V1.8 Added Time set with '!' and UART-RX-Error
  • V2.0 (nRf52) Changed UART Driver to APP_UART for Multi-Use in tb_tools
  • V2.01 (nRf52) Changed toSDK17 (problem with nrf_clock() in SDK17, see docu)
  • V2.02 (nRf52) Changed toSDK17.0.2 and SES 5,10b (problem with nrf_clock() in SDK17.0.2 not fixed in SDK17.0.2, see docu)

Using JesFs – BlackBox-Demo

A Flight Recorder for Home Use

Many technical devices work reliable for years and years and no one cares about them. But if they fail, there is always the question: WHAT WENT WRONG?

This is, where the JesFs could become extremely useful.

Read more: BlackBox_Eval.pdf


Jo's Embedded Serial File System (for Standard Serial NOR-Flash)

Jesfs Info

⭐ Stars 92
🔗 Homepage
🔗 Source Code
🕒 Last Update a year ago
🕒 Created 4 years ago
🐞 Open Issues 2
➗ Star-Issue Ratio 46
😎 Author joembedded