int main(void)
{
        NVSInit();

        return 0;
}



void NVSInit(){
	printk("\nNVS init started...\n");

	/* define the nvs file system by settings with:
	 *	sector_size equal to the pagesize,
	 *	3 sectors
	 *	starting at NVS_PARTITION_OFFSET
	 */
	fs.flash_device = NVS_PARTITION_DEVICE;
	if (!device_is_ready(fs.flash_device)) {
		printk("\n--ERROR: Flash device %s is not ready--\n", fs.flash_device->name);
		exit(1);
	}
	fs.offset = NVS_PARTITION_OFFSET;
	rc = flash_get_page_info_by_offs(fs.flash_device, fs.offset, &info);
	if (rc) {
		printk("\n--REEOR: Unable to get page info--\n");
		exit(1);
	}
	fs.sector_size = info.size;
	fs.sector_count = 3U;    
	printk("info.size = %d\n",fs.sector_size);
	printk("sector_size = %d\n",fs.sector_size);      

	rc = nvs_mount(&fs);
	if (rc) {
		printk("\n--ERROR: Flash Init failed--\n");
		exit(1);
	}
	else{
		printk("Successful init flash NVS.\n");
	}

	NVSRead();
	NVSWrite();
	NVSRead();
}


void NVSRead(){
	printk("\nRead data from NVS...\n");
	uint8_t* reading;
	rc = nvs_read(&fs, HALF_HOUR_VOLUME_READ_ID, &reading, 1);
	if (rc == 1){ /* item was found, show it */
		printk("Find NVS storage data: Id = %d, reading = %d\n", HALF_HOUR_VOLUME_READ_ID, reading);
		rc = 0;
	}
	else {/* item was not found, add it */
		printk("\nNo NVS storage data found at NVS id %d.\n", HALF_HOUR_VOLUME_READ_ID);
	}
}


void NVSWrite(){
	printk("\nWrite data to NVS...\n");
	uint8_t* data = 1000;
	rc = nvs_write(&fs, HALF_HOUR_VOLUME_READ_ID, &data, 1);
	if (rc == 1){ /* item was found, show it */
		printk("Successful write data = %d to NVS id %d\n", data, HALF_HOUR_VOLUME_READ_ID);
		rc = 0;
	}
	else {/* item was not found, add it */
		printk("\n--ERROR: Failed to write data to NVS id %d\n", HALF_HOUR_VOLUME_READ_ID);
	}
}





result:

-----------------first time running-------------------
No NVS storage data found at NVS id 2

Write data to NVS...
Successful write data = 1000 to NVS id 2
Find NVS storage data: Id = 2, reading = 1000


---------------------after reset:---------------------
Find NVS storage data: Id = 2, reading = 232

Write data to NVS...
Successful write data = 1000 to NVS id 2
Find NVS storage data: Id = 2, reading = 1000