esp-idf/examples/storage/fatfsgen/README.md

Supported Targets	ESP32	ESP32-C3	ESP32-C6	ESP32-H2	ESP32-P4	ESP32-S2	ESP32-S3

FATFS partition generation example

(See the README.md file in the upper level 'examples' directory for more information about examples.)

This example demonstrates how to use the FATFS partition generation tool fatfsgen.py to automatically create a FATFS filesystem image from the contents of a host folder during build, with an option of automatically flashing the created image on invocation of idf.py -p PORT flash. Beware that the minimal required size of the flash is 4 MB. You can specify using menuconfig weather example will use read-only or read-write mode. The default option is read-write mode. To change it just use menuconfig:

idf.py menuconfig

Then select Example Configuration a chose Mode for generated FATFS image either Read-Write Mode or Read-Only Mode. Read-Only option indicates generating raw fatfs image without wear levelling support. On the other hand, for Read-Write the generated fatfs image will support wear levelling thus can be mounted in read-write mode.

The following gives an overview of the example:

1. There is a directory fatfs_image from which the FATFS filesystem image will be created.

2. The function fatfs_create_rawflash_image is used to specify that a FATFS image should be created during build for the storage partition. For CMake, it is called from the main component's CMakeLists.txt. FLASH_IN_PROJECT specifies that the created image should be flashed on invocation of idf.py -p PORT flash together with app, bootloader, partition table, etc. The image is created on the example's build directory with the output filename storage.bin.

3. Upon invocation of idf.py -p PORT flash monitor, application loads and finds there is already a valid FATFS filesystem in the storage partition with files same as those in fatfs_image directory. The application is then able to read those files.

How to use example

Build and flash

To run the example, type the following command:

# CMake
idf.py -p PORT flash monitor

(To exit the serial monitor, type Ctrl-].)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

Example output

Here is the example's console output:

...
I (322) example: Mounting FAT filesystem
I (332) example: Reading file
I (332) example: Read from file: 'this is test'
I (332) example: Unmounting FAT filesystem
I (342) example: Done

The logic of the example is contained in a single source file, and it should be relatively simple to match points in its execution with the log outputs above.