In this video I am showing how to store a string into the NVS partition of an ESP32. I am mainly trying to do videos of subjects that I have noticed do not seem to have much coverage on YouTube. When I tried to look up some videos on this subject, I could only find one and in this one the main thing that happened was that they mainly just showed the example that was mentioned on the Espressif documentation website, so I decided to do a video relating to a data type that was not mentioned. I also show how to then update the data that has been stored in the NVS and that this data is preserved when the microcontroller is power cycled.

/* Non-Volatile Storage (NVS) Read and Write a Value - Example

   For other examples please check:
   https://github.com/espressif/esp-idf/tree/master/examples

   This example code is in the Public Domain (or CC0 licensed, at your option.)

   Unless required by applicable law or agreed to in writing, this
   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   CONDITIONS OF ANY KIND, either express or implied.
*/
#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_system.h"
#include "nvs_flash.h"
#include "nvs.h"
#include <string.h>

void app_main()
{
    // Initialize NVS
    esp_err_t err = nvs_flash_init();
    if (err == ESP_ERR_NVS_NO_FREE_PAGES || err == ESP_ERR_NVS_NEW_VERSION_FOUND) {
        // NVS partition was truncated and needs to be erased
        // Retry nvs_flash_init
        ESP_ERROR_CHECK(nvs_flash_erase());
        err = nvs_flash_init();
    }
    ESP_ERROR_CHECK( err );

    // Open
    printf("\n");
    printf("Opening Non-Volatile Storage (NVS) handle... ");
    nvs_handle my_handle;
    err = nvs_open("storage", NVS_READWRITE, &amp;my_handle);
    if (err != ESP_OK) {
        printf("Error (%s) opening NVS handle!\n", esp_err_to_name(err));
    } else {
        printf("Done\n");

        // Read
        printf("Reading string from NVS ... ");
        char buffer[1000];
        int textsize = 0;
        char test_string[] = "Here is a load of text to test the NVS string storage. ";
        size_t required_size;
        err = nvs_get_str(my_handle, "buffer", NULL, &amp;required_size );
        err = nvs_get_str(my_handle, "buffer", (char *)&amp;buffer, &amp;required_size);
        switch (err) {
        case ESP_OK:
            printf("Done\n\n");
            printf("Buffer = %s\n\n", buffer);
            break;
        case ESP_ERR_NVS_NOT_FOUND:
            printf("The value is not initialized yet!\n");
            memset(buffer, 0, sizeof(buffer));
            break;
        default :
            printf("Error (%s) reading!\n", esp_err_to_name(err));
        }
        textsize = strlen(buffer);
        printf("Buffer is %d characters in size\n", textsize);
        if (textsize &gt; 940) {
            printf("Text is getting too large, so restarting the ESP32!\n\n");
            for (int i = 6; i &gt;= 0; i--) {
                printf("Restarting in %d seconds...\n", i);
                vTaskDelay(1000 / portTICK_PERIOD_MS);
            }
            esp_restart();
        }

        // Write
        printf("Adding text to NVS ... ");
        strncat(buffer, (const char*)test_string, sizeof(test_string));
        err = nvs_set_str(my_handle, "buffer", (const char*)buffer);
        printf((err != ESP_OK) ? "Failed!\n" : "Done\n");

        // Commit written value.
        // After setting any values, nvs_commit() must be called to ensure changes are written
        // to flash storage. Implementations may write to storage at other times,
        // but this is not guaranteed.
        printf("Committing updates in NVS ... ");
        err = nvs_commit(my_handle);
        printf((err != ESP_OK) ? "Failed!\n" : "Done\n");

        // Close
        nvs_close(my_handle);
    }

    printf("\n");

    // Restart module
    for (int i = 4; i &gt;= 0; i--) {
        printf("Restarting in %d seconds...\n", i);
        vTaskDelay(1000 / portTICK_PERIOD_MS);
    }
    printf("Restarting now.\n");
    fflush(stdout);
    esp_restart();
}