Fu Hanxi a73b0c3eb6 ci: Modify some dut-unrelated example tests env tag from Example_WIFI to Example_GENERIC		5 years ago
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main	afbaf74007 tools: Mass fixing of empty prototypes (for -Wstrict-prototypes)	6 years ago
CMakeLists.txt	d9939cedd9 cmake: make main a component again	7 years ago
Makefile	382999b378 Moved examples to new folders / categories. Removed example numbers from example names	9 years ago
README.md	47bbb107a8 build system: Use CMake-based build system as default when describing commands	6 years ago
nvs_rw_value_example_test.py	a73b0c3eb6 ci: Modify some dut-unrelated example tests env tag from Example_WIFI to Example_GENERIC	5 years ago

Non-Volatile Storage (NVS) Read and Write Example

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

This example demonstrates how to read and write a single integer value using NVS.

In this example, value which is saved holds the number of ESP32 module restarts. Since it is written to NVS, the value is preserved between restarts.

Example also shows how to check if read / write operation was successful, or certain value is not initialized in NVS. Diagnostic is provided in plain text to help track program flow and capture any issues on the way.

Detailed functional description of NVS and API is provided in documentation.

Check another example storage/nvs_rw_blob, which shows how to read and write variable length binary data (blob).

How to use example

Hardware required

This example does not require any special hardware, and can be run on any common development board.

Build and flash

Build the project and flash it to the board, then run monitor tool to view serial output:

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

First run:

Opening Non-Volatile Storage (NVS) handle... Done
Reading restart counter from NVS ... The value is not initialized yet!
Updating restart counter in NVS ... Done
Committing updates in NVS ... Done

Restarting in 10 seconds...
Restarting in 9 seconds...
Restarting in 8 seconds...
Restarting in 7 seconds...
Restarting in 6 seconds...
Restarting in 5 seconds...
Restarting in 4 seconds...
Restarting in 3 seconds...
Restarting in 2 seconds...
Restarting in 1 seconds...
Restarting in 0 seconds...
Restarting now.

Subsequent runs:

Opening Non-Volatile Storage (NVS) handle... Done
Reading restart counter from NVS ... Done
Restart counter = 1
Updating restart counter in NVS ... Done
Committing updates in NVS ... Done

Restarting in 10 seconds...
Restarting in 9 seconds...
Restarting in 8 seconds...
Restarting in 7 seconds...
Restarting in 6 seconds...
Restarting in 5 seconds...
Restarting in 4 seconds...
Restarting in 3 seconds...
Restarting in 2 seconds...
Restarting in 1 seconds...
Restarting in 0 seconds...
Restarting now.

Restart counter will increment on each run.

To reset the counter, erase the contents of flash memory using idf.py erase_flash, then upload the program again as described above.