🛠 Remonter des données machine en MQTT via Ethernet

Objectives

Connect the Opta to an MQTT broker to report machine status to a supervisor (Node-RED, Mosquitto, Tasmota, cloud). The embedded 10/100 Ethernet ensures a reliable link in the workshop; the MQTT protocol, lightweight and publish/subscribe, is the IIoT standard. You will publish digital inputs every second to a hierarchical topic.

Hardware

• Arduino Opta powered by 24 VDC, Ethernet cable
• An accessible MQTT broker (Mosquitto on a Raspberry Pi or your chosen server)
• A test MQTT client (MQTT Explorer, mosquitto_sub)
• Arduino IDE + "Ethernet" and "PubSubClient" libraries

Complete code

// opta_mqtt.ino — publication des entrees I1..I4 en MQTT sur Ethernet
#include <Ethernet.h>
#include <PubSubClient.h>

EthernetClient ethClient;
PubSubClient mqtt(ethClient);

const char* BROKER = "192.168.1.50"; // IP de votre broker Mosquitto
const int ENTREES[] = {A0, A1, A2, A3}; // bornes I1..I4
char topic[40], payload[8];

void setup {
  Serial.begin(9600);
  if (Ethernet.begin == 0) { Serial.println("Echec DHCP"); while (1); }
  Serial.println(Ethernet.localIP);
  mqtt.setServer(BROKER, 1883);
  for (int i = 0; i < 4; i++) pinMode(ENTREES[i], INPUT);
}

void boucleMqtt {
  while (!mqtt.connected) {
    if (mqtt.connect("opta-atelier")) { Serial.println("MQTT connecte"); return; }
    delay(2000); // nouvelle tentative toutes les 2 s
  }
}

void loop {
  boucleMqtt;
  for (int i = 0; i < 4; i++) {
    snprintf(topic, sizeof(topic), "usine/opta1/E%d", i + 1);
    snprintf(payload, sizeof(payload), "%d", digitalRead(ENTREES[i]) ? 1 : 0);
    mqtt.publish(topic, payload, true); // retain = true
  }
  mqtt.loop;
  delay(1000);
}

Expected verification

With mosquitto_sub -t 'usine/opta1/#', messages usine/opta1/E1 = 0/1 scroll every second and follow your 24 V inputs. The retain flag allows the supervisor to know the last state as soon as it connects.

Common errors

• Broker unreachable: check firewall and port 1883; the serial port displays the IP, test ping before blaming the sketch.
• Forgetting mqtt.loop: without it, keep-alive messages are not sent and the broker disconnects the Opta every minute.
• Flooding the network: publishing on every loop iteration without timing saturates the broker; pace it (1 Hz is sufficient for states).
• MQTT without TLS in production: port 1883 is unencrypted; for a corporate network, document segmentation or use Arduino Cloud / AWS IoT, for which official Opta tutorials exist.