1# Wear levelling example
2
3(See the README.md file in the upper level 'examples' directory for more information about examples.)
4
5This example demonstrates how to use wear levelling library and FATFS library to store files in a partition inside SPI flash. Example does the following steps:
6
71. Use an "all-in-one" `esp_vfs_fat_spiflash_mount` function to:
8    - find a partition in SPI flash,
9    - initialize wear levelling library using this partition
10    - mount FAT filesystem using FATFS library (and format the filesystem, if the filesystem can not be mounted),
11    - register FAT filesystem in VFS, enabling C standard library and POSIX functions to be used.
122. Create a file using `fopen` and write to it using `fprintf`.
133. Open file for reading, read back the line, and print it to the terminal.
14
15Wear levelling partition size is set in partitions_example.csv file. See [Partition Tables](https://docs.espressif.com/projects/esp-idf/en/latest/api-guides/partition-tables.html) documentation for more information.
16
17## How to use example
18
19### Hardware required
20
21This example does not require any special hardware, and can be run on any common development board.
22
23### Build and flash
24
25Build the project and flash it to the board, then run monitor tool to view serial output:
26
27```
28idf.py -p PORT flash monitor
29```
30
31(Replace PORT with serial port name.)
32
33(To exit the serial monitor, type ``Ctrl-]``.)
34
35See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
36
37## Example output
38
39Here is a typical example console output.
40
41```
42I (280) example: Mounting FAT filesystem
43W (440) vfs_fat_spiflash: f_mount failed (13)
44I (440) vfs_fat_spiflash: Formatting FATFS partition, allocation unit size=4096
45I (660) vfs_fat_spiflash: Mounting again
46I (660) example: Opening file
47I (910) example: File written
48I (910) example: Reading file
49I (920) example: Read from file: 'written using ESP-IDF v3.1-dev-171-gf9ad17eee-dirty'
50I (920) example: Unmounting FAT filesystem
51I (1000) example: Done
52```
53
54To erase the contents of wear levelling partition, run `idf.py erase-flash` command. Then upload the example again as described above.
55