实物摆放提示：

1. 将 ESP32 竖插在面包板中央长槽两侧；
2. DHT22 放置在面包板左侧，栅格孔位方便上拉电阻的跨接；
3. OLED 屏插在右侧，I2C 走线尽量短，避免长线干扰；
4. DHT22 探头面朝外，远离 ESP32 的散热区（Wi-Fi 模组会轻微发热，影响测温）。

四、完整代码（Arduino 框架）

4.1 库依赖

在 Arduino IDE 中安装以下库：

• DHT sensor library（Adafruit）
• Adafruit Unified Sensor
• Adafruit SSD1306
• PubSubClient（Nick O'Leary）
• WiFi（ESP32 内置）

4.2 源码

/*********************************************************************
 *  ESP32 智能环境监测站
 *  功能：DHT22 温湿度采集 + SSD1306 OLED 显示 + MQTT 上报
 *  作者：AI Know 编辑部
 *  平台：Arduino-ESP32 v2.0.14+
 *********************************************************************/

#include <WiFi.h>
#include <PubSubClient.h>
#include <DHT.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

// ====== 用户配置区 ======
const char* WIFI_SSID     = "your_wifi_ssid";
const char* WIFI_PASS     = "your_wifi_password";
const char* MQTT_SERVER   = "broker.emqx.io";   // 公网测试 Broker
const int   MQTT_PORT     = 1883;
const char* MQTT_CLIENTID = "esp32_env_001";
const char* MQTT_TOPIC    = "home/livingroom/env";

// ====== 硬件引脚 ======
#define DHT_PIN   4
#define DHT_TYPE  DHT22

// ====== OLED 配置 ======
#define SCREEN_W 128
#define SCREEN_H 64
#define OLED_ADDR 0x3C
#define OLED_RST  -1   // 多数开发板无 RST 引脚
Adafruit_SSD1306 display(SCREEN_W, SCREEN_H, &Wire, OLED_RST);

// ====== 全局对象 ======
DHT dht(DHT_PIN, DHT_TYPE);
WiFiClient espClient;
PubSubClient mqtt(espClient);

float g_temp = 0.0, g_humi = 0.0;
unsigned long g_lastSample = 0;
const unsigned long SAMPLE_INTERVAL = 5000;   // 5 秒采集一次

// ====== 函数声明 ======
void connectWiFi();
void connectMQTT();
void readSensor();
void updateOLED();
void publishData();

// =================== 主程序 ===================
void setup() {
  Serial.begin(115200);
  delay(500);
  Serial.println("\n[BOOT] ESP32 环境监测站启动");

  // OLED 初始化
  if (!display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDR)) {
    Serial.println("[ERR] OLED 初始化失败");
    while (true);
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.display();

  // 传感器初始化
  dht.begin();

  // 网络初始化
  connectWiFi();
  mqtt.setBufferSize(512);
}

// FreeRTOS 风格的循环调度
void loop() {
  unsigned long now = millis();

  if (now - g_lastSample >= SAMPLE_INTERVAL) {
    g_lastSample = now;
    readSensor();
    updateOLED();
  }

  if (!mqtt.connected()) {
    connectMQTT();
  }
  mqtt.loop();

  publishData();
  delay(100);
}

// =================== 子函数 ===================
void connectWiFi() {
  Serial.printf("[WiFi] 连接中: %s", WIFI_SSID);
  WiFi.mode(WIFI_STA);
  int retry = 0;
  while (WiFi.status() != WL_CONNECTED && retry < 30) {
    delay(500);
    Serial.print(".");
    retry++;
  }
  if (WiFi.status() == WL_CONNECTED) {
    Serial.printf("\n[WiFi] 已连接, IP: %s\n", WiFi.localIP().toString().c_str());
  } else {
    Serial.println("\n[WiFi] 连接失败，请检查 SSID / 密码");
  }
}

void connectMQTT() {
  while (!mqtt.connected()) {
    Serial.print("[MQTT] 连接 Broker...");
    if (mqtt.connect(MQTT_CLIENTID)) {
      Serial.println("OK");
      mqtt.publish("home/livingroom/status", "online");
    } else {
      Serial.printf("失败 rc=%d, 5 秒后重试\n", mqtt.state());
      delay(5000);
    }
  }
}

void readSensor() {
  float t = dht.readTemperature();
  float h = dht.readHumidity();
  if (isnan(t) || isnan(h)) {
    Serial.println("[WARN] DHT22 读取失败，使用上一次值");
    return;
  }
  g_temp = t;
  g_humi = h;
  Serial.printf("[SENSOR] T=%.1f C, H=%.1f %%\n", g_temp, g_humi);
}

void updateOLED() {
  display.clearDisplay();
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.println("=== Env Station ===");
  display.printf("Temp : %.1f C\n", g_temp);
  display.printf("Humi : %.1f %%\n", g_humi);

  // 简易温湿度条形图
  display.setCursor(0, 32);
  display.print("T: ");
  display.println(String((int)(g_temp + 40) / 1).c_str());  // 0~80℃ 映射
  display.setCursor(0, 44);
  display.print("H: ");
  int bar = (int)(g_humi / 100.0 * 80);
  for (int i = 0; i < bar; i++) display.print((char)0xFF);
  display.display();
}

void publishData() {
  static unsigned long lastPub = 0;
  if (millis() - lastPub < 10000) return;   // 10 秒上报一次
  lastPub = millis();

  if (!mqtt.connected()) return;

  char payload[160];
           "{\"device\":\"%s\",\"temp\":%.1f,\"humi\":%.1f,"
           "\"rssi\":%d,\"uptime\":%lu}",
           MQTT_CLIENTID, g_temp, g_humi,
           WiFi.RSSI(), millis() / 1000);

  if (mqtt.publish(MQTT_TOPIC, payload)) {
    Serial.printf("[MQTT] 上报成功: %s\n", payload);
  } else {
    Serial.println("[MQTT] 上报失败");
  }
}

[BOOT] ESP32 环境监测站启动       ← 启动正常
[WiFi] 已连接, IP: 192.168.1.42   ← 网络 OK
[MQTT] 连接 Broker...OK            ← Broker OK
[SENSOR] T=25.3 C, H=58.2 %        ← 传感器正常
[MQTT] 上报成功: {"device":...}    ← 链路打通

mqtt:
  sensor:
    - name: "客厅温度"
      state_topic: "home/livingroom/env"
      value_template: "{{ value_json.temp }}"
      unit_of_measurement: "°C"
    - name: "客厅湿度"
      state_topic: "home/livingroom/env"
      value_template: "{{ value_json.humi }}"
      unit_of_measurement: "%"

esp_sleep_enable_timer_wakeup(300 * 1000000ULL); // 5 分钟
esp_deep_sleep_start();