Wifi Mqtt Gateway

July 15, 2023

Developing a Wifi-Mqtt-Gateway #

What does it do? #

The gateway receives serial data from micro-inverters over 2.4ghz, generates a message that is published via Wifi to the mosquitto mqtt broker. In Node-Red we subscribe to the topic power/inverter and receive the message generated and sent by the mqtt broker.

Code sample. #

The following tutorials can be a source for information.

• Raspberry Pi IoT Server Tutorial: InfluxDB, MQTT, Grafana, Node-RED & Docker
• Simple ESP32 IoT Sensor Node Tutorial: WiFi Enabled MQTT Sensor Data Node

#include <WiFi.h>
#include <PubSubClient.h>

// Replace the next variables with your SSID/Password combination
const char* ssid = "XXXXXXXX";
const char* password = "XXXXXXXX";


// Add your MQTT Broker IP address, example:
//const char* mqtt_server = "192.168.1.144";
const char* mqtt_server = "192.168.178.138";
const char* mqtt_username = "XXXXXXX";
const char* mqtt_password = "XXXXXXX";


WiFiClient espClient;
PubSubClient client(espClient);
long lastMsg = 0;
char msg[50];
int value = 0;

// LED Pin
const int ledPin = 4;

void setup() {
  Serial.begin(115200);  
  setup_wifi();
  client.setServer(mqtt_server, 1883);

  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 reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Attempt to connect
    if (client.connect("ESP8266Client",mqtt_username,mqtt_password)) {
      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;
    const char* testString = "Hello MQTT";
    
    Serial.println(testString);
    client.publish("power/test", testString);
  }
}