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ESP MQTT

/*********
Rui Santos
Complete project details at https://randomnerdtutorials.com
*********/
#include <WiFi.h>
#include <PubSubClient.h>
#include <Wire.h>
#include <Adafruit_BME280.h>
#include <Adafruit_Sensor.h>
// Replace the next variables with your SSID/Password combination
const char* ssid = "REPLACE_WITH_YOUR_SSID";
const char* password = "REPLACE_WITH_YOUR_PASSWORD";
// Add your MQTT Broker IP address, example:
//const char* mqtt_server = "192.168.1.144";
const char* mqtt_server = "YOUR_MQTT_BROKER_IP_ADDRESS";
WiFiClient espClient;
PubSubClient client(espClient);
long lastMsg = 0;
char msg[50];
int value = 0;
//uncomment the following lines if you're using SPI
/*#include <SPI.h>
#define BME_SCK 18
#define BME_MISO 19
#define BME_MOSI 23
#define BME_CS 5*/
Adafruit_BME280 bme; // I2C
//Adafruit_BME280 bme(BME_CS); // hardware SPI
//Adafruit_BME280 bme(BME_CS, BME_MOSI, BME_MISO, BME_SCK); // software SPI
float temperature = 0;
float humidity = 0;
// LED Pin
const int ledPin = 4;
void setup() {
Serial.begin(115200);
// default settings
// (you can also pass in a Wire library object like &Wire2)
//status = bme.begin();
if (!bme.begin(0x76)) {
Serial.println("Could not find a valid BME280 sensor, check wiring!");
while (1);
}
setup_wifi();
client.setServer(mqtt_server, 1883);
client.setCallback(callback);
pinMode(ledPin, OUTPUT);
}
void setup_wifi() {
delay(10);
// We start by connecting to a WiFi network
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();
// Feel free to add more if statements to control more GPIOs with MQTT
// If a message is received on the topic esp32/output, you check if the message is either "on" or "off".
// Changes the output state according to the message
if (String(topic) == "esp32/output") {
Serial.print("Changing output to ");
if(messageTemp == "on"){
Serial.println("on");
digitalWrite(ledPin, HIGH);
}
else if(messageTemp == "off"){
Serial.println("off");
digitalWrite(ledPin, LOW);
}
}
}
void reconnect() {
// Loop until we're reconnected
while (!client.connected()) {
Serial.print("Attempting MQTT connection...");
// Attempt to connect
if (client.connect("ESP8266Client")) {
Serial.println("connected");
// Subscribe
client.subscribe("esp32/output");
} else {
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 5 seconds");
// Wait 5 seconds before retrying
delay(5000);
}
}
}
void loop() {
if (!client.connected()) {
reconnect();
}
client.loop();
long now = millis();
if (now - lastMsg > 5000) {
lastMsg = now;
// Temperature in Celsius
temperature = bme.readTemperature();
// Uncomment the next line to set temperature in Fahrenheit
// (and comment the previous temperature line)
//temperature = 1.8 * bme.readTemperature() + 32; // Temperature in Fahrenheit
// Convert the value to a char array
char tempString[8];
dtostrf(temperature, 1, 2, tempString);
Serial.print("Temperature: ");
Serial.println(tempString);
client.publish("esp32/temperature", tempString);
humidity = bme.readHumidity();
// Convert the value to a char array
char humString[8];
dtostrf(humidity, 1, 2, humString);
Serial.print("Humidity: ");
Serial.println(humString);
client.publish("esp32/humidity", humString);
}
}

Subscribing to MQTT topics

In the reconnect() function, you can subscribe to MQTT topics. In this case, the ESP32 is only subscribed to the esp32/output:
client.subscribe("esp32/output");
In the callback() function, the ESP32 receives the MQTT messages of the subscribed topics. According to the MQTT topic and message, it turns the LED on or off:
// If a message is received on the topic esp32/output, you check if the message is either "on" or "off".
// Changes the output state according to the message
if (String(topic) == "esp32/output") {
Serial.print("Changing output to ");
if (messageTemp == "on") {
Serial.println("on");
digitalWrite(ledPin, HIGH);
}
else if (messageTemp == "off") {
Serial.println("off");
digitalWrite(ledPin, LOW);
}
}

Publishing MQTT messages

In the loop(), new readings are being published every 5 seconds:
if (now - lastMsg > 5000) { ... }
By default the ESP32 is sending the temperature in Celsius, but you can uncomment the last line to send the temperature in Fahrenheit:
// Temperature in Celsius
temperature = bme.readTemperature();
// Uncomment the next line to set temperature in Fahrenheit
// (and comment the previous temperature line)
//temperature = 1.8 * bme.readTemperature() + 32; // Temperature in Fahrenheit
You need to convert the temperature float variable to a char array, so that you can publish the temperature reading in the esp32/temperature topic:
// Convert the value to a char array
char tempString[8];
dtostrf(temperature, 1, 2, tempString);
Serial.print("Temperature: ");
Serial.println(tempString);
client.publish("esp32/temperature", tempString);
The same process is repeated to publish the humidity reading in the esp32/humidity topic:
humidity = bme.readHumidity();
// Convert the value to a char array
char humString[8];
dtostrf(humidity, 1, 2, humString);
Serial.print("Humidity: ");
Serial.println(humString);
client.publish("esp32/humidity", humString);