ESP32 数据存哪里？NVS、小文件和 SD 卡分别适合什么

idf.py --version
# 项目根目录；ESP-IDF v5.5.5
idf.py set-target esp32s3
idf.py build
idf.py -p REPLACE_WITH_UART_PORT flash monitor
# 在串口逐行输入；先查状态，再有意选择需要的操作
status
set 3000
save
# SD变体：menuconfig -> Storage lesson -> DEMO_USE_SD；新build目录重建
# idf.py -B build-sd menuconfig
# idf.py -B build-sd build

/* SPDX-License-Identifier: MIT */
#include <stdio.h>
#include <string.h>
#include <inttypes.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/semphr.h"
#include "driver/spi_common.h"
#include "driver/sdspi_host.h"
#include "esp_log.h"
#include "esp_timer.h"
#include "esp_random.h"
#include "esp_spiffs.h"
#include "esp_vfs_fat.h"
#include "sdmmc_cmd.h"
#include "nvs_flash.h"
#include "nvs.h"
#include "sdkconfig.h"
#include "storage_model.h"
#include "journal.h"
static const char *TAG="storage_lesson";
static SemaphoreHandle_t mutex;
static uint32_t interval_ms=2000, sequence, boot_id;
static bool mounted, stopped, nvs_ready;
static size_t log_bytes;
#if CONFIG_DEMO_USE_SD
static const char *path="/sd/samples.csv";
#else
static const char *path="/data/samples.csv";
#endif
static uint32_t load_config(void) {
 nvs_handle_t h;esp_err_t e=nvs_open("store_demo",NVS_READONLY,&h);
 if(e==ESP_ERR_NVS_NOT_FOUND){ESP_LOGI(TAG,"NVS_MISSING: defaults=2000ms, no automatic save");return 2000;}
 if(e!=ESP_OK){ESP_LOGE(TAG,"NVS_OPEN=%s",esp_err_to_name(e));return 2000;}
 uint8_t b[8];size_t n=sizeof(b);e=nvs_get_blob(h,"config",b,&n);nvs_close(h);uint32_t ms;
 if(e==ESP_OK && config_decode(b,n,&ms))return ms;
 ESP_LOGW(TAG,"NVS_MISSING_OR_INVALID=%s size=%u, defaults remain unsaved",esp_err_to_name(e),(unsigned)n);return 2000;
}
static esp_err_t save_config(void) {
 if(!nvs_ready)return ESP_ERR_INVALID_STATE;
 uint8_t b[8];config_encode(interval_ms,b);nvs_handle_t h;esp_err_t e=nvs_open("store_demo",NVS_READWRITE,&h);
 if(e!=ESP_OK)return e;
 e=nvs_set_blob(h,"config",b,sizeof(b));if(e==ESP_OK)e=nvs_commit(h);nvs_close(h);return e;
}
static esp_err_t mount_files(void) {
#if CONFIG_DEMO_USE_SD
 sdmmc_host_t host=SDSPI_HOST_DEFAULT();host.max_freq_khz=10000;
 spi_bus_config_t bus={.mosi_io_num=11,.miso_io_num=13,.sclk_io_num=12,.quadwp_io_num=-1,.quadhd_io_num=-1,.max_transfer_sz=4000};
 esp_err_t e=spi_bus_initialize(host.slot,&bus,SDSPI_DEFAULT_DMA);if(e!=ESP_OK)return e;
 sdspi_device_config_t device=SDSPI_DEVICE_CONFIG_DEFAULT();device.gpio_cs=10;device.host_id=host.slot;
 esp_vfs_fat_sdmmc_mount_config_t config={.format_if_mount_failed=false,.max_files=3,.allocation_unit_size=16*1024};
 sdmmc_card_t *card=NULL;e=esp_vfs_fat_sdspi_mount("/sd",&host,&device,&config,&card);
 if(e==ESP_OK)sdmmc_card_print_info(stdout,card);else spi_bus_free(host.slot);
 return e;
#else
 esp_vfs_spiffs_conf_t config={.base_path="/data",.partition_label="logs",.max_files=3,.format_if_mount_failed=false};
 return esp_vfs_spiffs_register(&config);
#endif
}
static void inspect_log(void) {
 log_bytes=0;sequence=0;stopped=false;
 FILE *file=fopen(path,"r");
 if(!file){if(errno==ENOENT){ESP_LOGI(TAG,"LOG_MISSING: first append will create it");return;}stopped=true;ESP_LOGE(TAG,"LOG_OPEN errno=%d",errno);return;}
 journal_result_t result=journal_scan(file,&log_bytes,&sequence);
 if(fclose(file)!=0)result=JOURNAL_IO_ERROR;
 if(result!=JOURNAL_OK){stopped=true;ESP_LOGE(TAG,"LOG_RECOVERY_REQUIRED result=%d: preserve original; no automatic truncate",result);}
 ESP_LOGI(TAG,"LOG_SCAN bytes=%u last_sequence=%"PRIu32" result=%d",(unsigned)log_bytes,sequence,result);
}
static void logger(void *unused) {
 (void)unused;
 for(;;) {
  xSemaphoreTake(mutex,portMAX_DELAY);uint32_t wait=interval_ms;
  if(mounted && !stopped) {
   char line[96];record_encode(boot_id,sequence+1,(uint64_t)(esp_timer_get_time()/1000),line,sizeof(line));
   FILE *file=fopen(path,"a");journal_result_t result=JOURNAL_IO_ERROR;
   if(file){result=journal_append(file,&log_bytes,line,fwrite);if(fclose(file)!=0)result=JOURNAL_IO_ERROR;}
   if(result==JOURNAL_OK){++sequence;ESP_LOGI(TAG,"APPEND seq=%"PRIu32" bytes=%u (not a power-cut durability proof)",sequence,(unsigned)log_bytes);}
   else {stopped=true;ESP_LOGE(TAG,"APPEND_STOP result=%d errno=%d: LIMIT=1, BAD_TAIL=2, IO=3; do not retry a possible partial tail",result,errno);}
  }
  xSemaphoreGive(mutex);vTaskDelay(pdMS_TO_TICKS(wait));
 }
}
static void status(void) {
 ESP_LOGI(TAG,"backend=%s mounted=%u stopped=%u NVS_ready=%u interval=%"PRIu32" bytes=%u cap=%u seq=%"PRIu32,path,mounted,stopped,nvs_ready,interval_ms,(unsigned)log_bytes,JOURNAL_LIMIT,sequence);
#if !CONFIG_DEMO_USE_SD
 if(mounted){size_t total,used;esp_err_t e=esp_spiffs_info("logs",&total,&used);ESP_LOGI(TAG,"SPIFFS info=%s total=%u used=%u (application cap is separate)",esp_err_to_name(e),(unsigned)(e==ESP_OK?total:0),(unsigned)(e==ESP_OK?used:0));}
#endif
}
void app_main(void) {
 mutex=xSemaphoreCreateMutex();if(!mutex)return;
 esp_err_t e=nvs_flash_init();nvs_ready=e==ESP_OK;
 if(nvs_ready)interval_ms=load_config();else ESP_LOGE(TAG,"NVS_INIT=%s: no automatic erase; file logging may still run with defaults",esp_err_to_name(e));
 e=mount_files();mounted=e==ESP_OK;ESP_LOGI(TAG,"MOUNT=%s; format_if_mount_failed=false",esp_err_to_name(e));
 if(mounted)inspect_log();
 boot_id=esp_random();
 if(xTaskCreate(logger,"append_log",4096,NULL,3,NULL)!=pdPASS){ESP_LOGE(TAG,"logger allocation failed");return;}
 ESP_LOGI(TAG,"Commands: status | set 1000..60000 | save | CLEAR LOG | FORMAT SPIFFS (destructive after backup)");
 char command[80];
 for(;;) {
  if(!fgets(command,sizeof(command),stdin)){clearerr(stdin);vTaskDelay(pdMS_TO_TICKS(100));continue;}
  size_t n=strcspn(command,"\r\n");command[n]=0;
  xSemaphoreTake(mutex,portMAX_DELAY);
  if(!strcmp(command,"status"))status();
  else if(!strncmp(command,"set ",4)){
   char *end;errno=0;unsigned long value=strtoul(command+4,&end,10);
   if(errno || end==command+4 || *end || value>UINT32_MAX || !interval_valid((uint32_t)value))ESP_LOGW(TAG,"SET_REJECTED");
   else {interval_ms=(uint32_t)value;ESP_LOGI(TAG,"runtime interval changed; use save for NVS");}
  } else if(!strcmp(command,"save")){e=save_config();ESP_LOGI(TAG,"NVS_SAVE=%s: failure does not erase or claim success",esp_err_to_name(e));}
  else if(!strcmp(command,"CLEAR LOG")){
   if(!mounted)ESP_LOGE(TAG,"Not mounted; no delete");
   else if(unlink(path)==0 || errno==ENOENT){stopped=false;log_bytes=0;sequence=0;ESP_LOGW(TAG,"Log cleared by explicit command");}
   else ESP_LOGE(TAG,"DELETE errno=%d",errno);
  } else if(!strcmp(command,"FORMAT SPIFFS")){
#if CONFIG_DEMO_USE_SD
   ESP_LOGW(TAG,"SD variant: formatting disabled; use computer after backup");
#else
   e=esp_spiffs_format("logs");ESP_LOGW(TAG,"EXPLICIT_FORMAT=%s",esp_err_to_name(e));
   if(e==ESP_OK){if(!mounted){e=mount_files();mounted=e==ESP_OK;}if(mounted)inspect_log();}
#endif
  } else ESP_LOGW(TAG,"Unknown command; no storage mutation");
  xSemaphoreGive(mutex);
 }
}

cc -std=c11 -D_POSIX_C_SOURCE=200809L -Wall -Wextra -Werror -I main host/host_check.c main/journal.c -o /tmp/e08-host
/tmp/e08-host