NVS (Non-Volatile Storage)

NVS is a library for storing and retrieving non-volatile key-value pairs. It is designed for small amounts of data (typically configuration parameters) that change occasionally, such as device configuration or calibration data.

Include

#include "nvs_flash.h"
#include "nvs.h"
#include "nvs_handle.hpp"

NVS Partition

NVS uses a dedicated partition to store data. The partition is created and formatted the first time the NVS is initialized.

Initialize NVS

esp_err_t err = nvs_flash_init(void);

if (err == ESP_ERR_NVS_NO_FREE_PAGES || err == ESP_ERR_NVS_NEW_VERSION_FOUND) {
    ESP_ERROR_CHECK(nvs_flash_erase());
    err = nvs_flash_init();
}

Read

nvs_handle_t my_handle;
esp_err_t err = nvs_open("storage", NVS_READWRITE, &my_handle);
if (err != ESP_OK) {
    printf("Error (%s) opening NVS handle!\n", esp_err_to_name(err));
    return;
}

// Read
int32_t value = 0; // value will default to 0, if not set yet in NVS
err = nvs_get_i32(my_handle, "storage", &value

// Close
nvs_close(my_handle);

Write

nvs_handle_t my_handle;
esp_err_t err = nvs_open("storage", NVS_READWRITE, &my_handle);
if (err != ESP_OK) {
    printf("Error (%s) opening NVS handle!\n", esp_err_to_name(err));
    return;
}

// Write
int32_t value = 0;
err = nvs_set_i32(my_handle, "storage", value);

// Commit
err = nvs_commit(my_handle);

// Close
nvs_close(my_handle);

Delete

nvs_handle_t my_handle;
esp_err_t err = nvs_open("storage", NVS_READWRITE, &my_handle);
if (err != ESP_OK) {
    printf("Error (%s) opening NVS handle!\n", esp_err_to_name(err));
    return;
}

// Delete
err = nvs_erase_key(my_handle, "storage");

// Commit
err = nvs_commit(my_handle);

// Close
nvs_close(my_handle);

Secure NVS

todo

reference

• ESP-IDF NVS