3.3 注意事项

• DHT22 数据线务必加上拉电阻，10KΩ 接 DATA 与 VCC 之间，否则长距离通信易出错。
• ESP32 GPIO 在启动时不要接高电平输入，IO4/IO21/IO22 均为安全引脚。
• OLED 屏幕 I2C 地址一般为 **0x3C**，若不显示可用 I2C Scanner 扫描确认。

四、完整代码（Arduino 框架）

4.1 安装依赖库

打开 Arduino IDE → 库管理器，搜索并安装以下库：

• **DHT sensor library** (Adafruit)
• **Adafruit Unified Sensor**
• **Adafruit SSD1306**
• **Adafruit GFX Library**
• **PubSubClient** (Nick O'Leary)

4.2 完整源码

/*********************************************************************
 *  ESP32 智能环境监测站
 *  功能：DHT22 温湿度采集 + OLED 显示 + MQTT 上云
 *  作者：AI Know
 *  平台：Arduino-ESP32 (esp32 by Espressif Systems 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 ============
const char* WIFI_SSID     = "your_wifi_ssid";
const char* WIFI_PASSWORD = "your_wifi_password";

const char* MQTT_SERVER   = "broker.emqx.io";   // 公共测试 Broker
const int   MQTT_PORT     = 1883;
const char* MQTT_CLIENT   = "esp32_env_station_01";
const char* MQTT_TOPIC    = "home/room1/env";

#define DHTPIN    4
#define DHTTYPE   DHT22

#define SDA_PIN   21
#define SCL_PIN   22
#define SCREEN_W  128
#define SCREEN_H  64

// ============ 对象初始化 ============
DHT dht(DHTPIN, DHTTYPE);
Adafruit_SSD1306 display(SCREEN_W, SCREEN_H, &Wire, -1);
WiFiClient espClient;
PubSubClient mqtt(espClient);

unsigned long lastSample = 0;
const unsigned long SAMPLE_INTERVAL = 5000;  // 5 秒采集一次

// ============ 函数声明 ============
void setupWifi();
void setupMqtt();
void callback(char* topic, byte* payload, unsigned int length);
void reconnect();
void readSensor(float &t, float &h, bool &ok);

// =================================================================
void setup() {
  Serial.begin(115200);
  delay(200);
  Serial.println("\n[BOOT] ESP32 Env Station Starting...");

  // I2C 初始化
  Wire.begin(SDA_PIN, SCL_PIN);

  // OLED 初始化
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    while (true);
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.display();

  // DHT 初始化
  dht.begin();

  // 网络
  setupWifi();
  setupMqtt();
}

// =================================================================
void loop() {
  if (!mqtt.connected()) reconnect();
  mqtt.loop();

  unsigned long now = millis();
  if (now - lastSample >= SAMPLE_INTERVAL) {
    lastSample = now;
    float temp, humi;
    bool ok;
    readSensor(temp, humi, ok);

    if (ok) {
      Serial.printf("[DATA] T=%.2f C  H=%.2f %%\n", temp, humi);
      publishData(temp, humi);
    } else {
    }
  }
}

// ============ WiFi 连接 ============
void setupWifi() {
  Serial.printf("[WIFI] Connecting to %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] OK, IP: %s\n", WiFi.localIP().toString().c_str());
  } else {
    Serial.println("\n[WIFI] FAIL, will retry in loop");
  }
}

// ============ MQTT 初始化 ============
void setupMqtt() {
  mqtt.setCallback(callback);
}

// ============ MQTT 回调（订阅消息处理）============
void callback(char* topic, byte* payload, unsigned int length) {
  Serial.printf("[MQTT] Recv [%s]: ", topic);
  for (unsigned int i = 0; i < length; i++) {
  }
  Serial.println();
  // 示例：根据指令切换本地 LED
  // if (String(topic) == "home/room1/cmd" && payload[0] == '1') { ... }
}

// ============ MQTT 重连 ============
void reconnect() {
  static unsigned long lastTry = 0;
  if (millis() - lastTry < 5000) return;
  lastTry = millis();

  if (mqtt.connected()) return;
  if (mqtt.connect(MQTT_CLIENT)) {
    Serial.println(" OK");
    mqtt.publish("home/room1/status", "online");
    mqtt.subscribe("home/room1/cmd");
  } else {
    Serial.printf(" FAIL rc=%d\n", mqtt.state());
  }
}

// ============ 传感器读取 ============
void readSensor(float &t, float &h, bool &ok) {
  float temp = dht.readTemperature();
  float humi = dht.readHumidity();
  if (isnan(temp) || isnan(humi)) {
    ok = false;
    t = 0; h = 0;
  } else {
    ok = true;
    t = temp; h = humi;
  }
}

// ============ OLED 显示 ============
void updateOled(float t, float h, bool wifiOk, bool mqttOk) {
  display.clearDisplay();
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.println("== Env Station ==");
  display.printf("Temp : %.1f C\n", t);
  display.printf("Humi : %.1f %%\n", h);
  display.setCursor(0, 34);
  display.printf("WiFi: %s\n", wifiOk ? "OK" : "NO");
  display.printf("MQTT: %s\n", mqttOk ? "ON" : "OFF");
  display.printf("RSSI: %d dBm", WiFi.RSSI());
  display.display();
}

// ============ 发布数据 ============
void publishData(float t, float h) {
  char payload[160];
  // 使用 JSON 格式，便于后端解析
           "{\"device\":\"%s\",\"temp\":%.2f,\"humi\":%.2f,\"rssi\":%d}",
  Serial.printf("[MQTT] Pub [%s]: %s\n", MQTT_TOPIC, payload);
}

if (WiFi.status() != WL_CONNECTED) {
  WiFi.reconnect();
}