ESP32教程46/55 - 使用HiveMQ MQTT进行远程温度监控 | SunFounder的ESP32套件

/*
 * :ref: https://randomnerdtutorials.com/esp32-mqtt-publish-subscribe-arduino-ide/  
 * https://docs.sunfounder.com/projects/kepler-kit/en/latest/iotproject/5.mqtt_pub.html
 */
#include <WiFi.h>
#include <PubSubClient.h>
 // #include <Wire.h>

 // 用您的SSID/密码组合替换下列变量。
const char* ssid = "SSID";
const char* password = "PASSWORD";

 // 添加您的 MQTT 代理地址，例如：
const char* mqtt_server = "broker.hivemq.com";
const char* unique_identifier = "sunfounder-client-sdgvsda";

WiFiClient espClient;
PubSubClient client(espClient);
long lastMsg = 0;
int value = 0;


 // LED引脚
const int ledPin = 4;
const int buttonPin = 14;

 // 当你连接到WIFI时，只有36、39、34、35、32、33引脚可以用于模拟读取。
 // 定义常量
const int thermistorPin = 36; // 连接到热敏电阻的引脚
const float referenceVoltage = 3.3;
const float referenceResistor = 10000; // 电阻值（10k）
const float beta = 3950; // 贝塔值（典型值）
const float nominalTemperature = 25; // 计算温度系数的名义温度
const float nominalResistance = 10000; // 在名义温度下的电阻值



void setup() {
  Serial.begin(115200);

 // 默认设置
  setup_wifi();
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);

  pinMode(buttonPin, INPUT);
  pinMode(ledPin, OUTPUT);
}

void setup_wifi() {
  delay(10);
 // 我们首先连接到一个WiFi网络。
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

void callback(char* topic, byte* message, unsigned int length) {
  Serial.print("Message arrived on topic: ");
  Serial.print(topic);
  Serial.print(". Message: ");
  String messageTemp;

  for (int i = 0; i < length; i++) {
    Serial.print((char)message[i]);
    messageTemp += (char)message[i];
  }
  Serial.println();

 // 如果在"SF/LED"主题上收到消息，你需要检查该消息是"开"还是"关"。
 // 根据消息更改输出状态。
  if (String(topic) == "SF/LED") {
    Serial.print("Changing state to ");
    if (messageTemp == "on") {
      Serial.println("on");
      digitalWrite(ledPin, HIGH);
    } else if (messageTemp == "off") {
      Serial.println("off");
      digitalWrite(ledPin, LOW);
    }
  }
}

void reconnect() {
 // 循环直到我们重新连接
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
 // 尝试连接
    if (client.connect(unique_identifier)) {
      Serial.println("connected");
 // 订阅
      client.subscribe("SF/LED");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
 // 请在重试之前等待5秒。
      delay(5000);
    }
  }
}

float thermistor() {
  int adcValue = analogRead(thermistorPin); // 读取ADC值
  float voltage = (adcValue * referenceVoltage) / 4095.0; // 计算电压
  float resistance = (voltage * referenceResistor) / (referenceVoltage - voltage); // 使用更新的配置计算热敏电阻电阻值

 // 使用贝塔参数方程计算温度
  float tempK = 1 / (((log(resistance / nominalResistance)) / beta) + (1 / (nominalTemperature + 273.15)));

  float tempC = tempK - 273.15; // 获取摄氏温度
  float tempF = 1.8 * tempC + 32.0; // 获取华氏温度

 // 打印温度
  Serial.print("Temp: ");
  Serial.println(tempC);
  delay(200); // 等待200毫秒
  return tempC;
}

void loop() {
  if (!client.connected()) {
    reconnect();
  }
  client.loop();

 // 如果按钮被按下，发布温度到主题 "SF/TEMP"
  if (digitalRead(buttonPin)) {
    long now = millis();
    if (now - lastMsg > 5000) {
      lastMsg = now;
      char tempString[8];
      dtostrf(thermistor(), 1, 2, tempString);
      client.publish("SF/TEMP", tempString);
    }
  }
}