ESP32 Forum

Posted: **Sat Sep 25, 2021 2:50 am**

Hi,

I have been trying to save a simple cjson data to nvs and read it back. I am kind of lost and would love if you could help me figure out what I am doing wrong. I want to add error (sent through parameter in the function) to be appended to the cjson message after each function call and print the cjson stored in nvs to see if everything is correct.

Thank you.

I have pasted the code in pastebin in the link below as well. I have commented it for clarity as well:

https://pastebin.com/4pNbF29b

Code: [Select all] [Expand/Collapse]

char* ErrorReporting(esp_err_t NodeError)
{
    ESP_LOGI(TAG, "NVS Error Reporting %d", NodeError);
    esp_err_t err;
        
    cJSON *cJNodeError = NULL;
 
    cJSON *cJnodeErrorObject = cJSON_CreateObject();                     //Create a cjson object
    cJNodeError = cJSON_CreateNumber(NodeError);                         //Create a cjson number to be added to the object
    cJSON_AddItemToObject(cJnodeErrorObject, "NodeError", cJNodeError);  //Adding the cjson number created to the object
    char *pNodeError = cJSON_PrintUnformatted(cJnodeErrorObject);        // Saving the cjson object into a variable.
    int LengthOfcJson = strlen(pNodeError);                              // Getting length of cJson
 
    ESP_LOGI(TAG, "Size of cJsonString... %d", LengthOfcJson);           //Printing the length of cjson
 
    // Open
    ESP_LOGI(TAG, "Opening Non-Volatile Storage (NVS) handle...");
    nvs_handle nvsHandle;                                                //Creating nvshandle
    err = nvs_open("nvsStorage", NVS_READWRITE, &nvsHandle);             //Opening the nvsStorage space for read and write
    if (err != ESP_OK)
    {
        ESP_LOGI(TAG, "Error (%s) opening NVS handle!", esp_err_to_name(err));     //Checking for errors in opening nvs
    }
    else
    {
        ESP_LOGI(TAG, "NVS Storage opened");                             
        // Read from NVS
        ESP_LOGI(TAG, "Reading string from NVS ...");
        size_t required_size = 0;
        err = nvs_get_blob(nvsHandle, "nvsbuffer", NULL, &required_size); //This reads if the nvsbuffer is initialized before or not
        int req_size = LengthOfcJson + required_size;                     //Calculating the total size of the data to be written
        char *run_buffer = (char*)malloc(req_size*sizeof(int));           //creating a buffer to read data from
        if (required_size > 0)
        {
            // The contents of nvsbuffer is saved in run_buffer and then is read from it
            err = nvs_get_blob(nvsHandle, "nvsbuffer", run_buffer, &required_size); 
            required_size += LengthOfcJson;
            
            //Writing cJnodeErrorObject json string to nvsbuffer
            err = nvs_set_blob(nvsHandle, "nvsbuffer", cJnodeErrorObject, required_size); 
 
            char *string = cJSON_Print(cJnodeErrorObject);           
            printf("The cjson value is: %s", string);         //print cJson 
 
            if (err != ESP_OK)
            {
                ESP_LOGI(TAG, "Error Setting string");
            }
 
            // Commit written value.
            ESP_LOGI(TAG, "Committing updates in NVS ...");
            err = nvs_commit(nvsHandle);
            if (err != ESP_OK)
            {
                ESP_LOGI(TAG, "Error Committing to NVS");
            }
 
            // Close the handle
            free(run_buffer);
            nvs_close(nvsHandle);
            return run_buffer;
        }
       
    }
    return 0;
}

Posted: **Mon Sep 27, 2021 3:01 am**

I think if you want to append error to old cjson stored in nvs, you need nvs_get_blob cjson data and append error to the buffer and than call nvs_set_blob to store buffer to nvs.

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