Davide Gomba
Published © MIT

Controllin Arduino MKR or ESP with Json via MQTT

We'll manage to control the basic behaviour of Arduino (or ESP based boards) using MQTT and the Arduino Json Library.

BeginnerProtip1 hour1,613
Controllin Arduino MKR or ESP with Json via MQTT

Things used in this project

Hardware components

Arduino MKR1000
Arduino MKR1000
×1
Arduino MKR WiFi 1010
Arduino MKR WiFi 1010
×1
Adafruit Feather HUZZAH with ESP8266 WiFi
Adafruit Feather HUZZAH with ESP8266 WiFi
×1

Software apps and online services

Arduino IDE
Arduino IDE
Node-RED
Node-RED
MQTT
MQTT
JSON

Story

Read more

Code

Minimal Json communication via MQTT and Node-RED

Arduino
/* This example shows how to use MQTT on the main dev boards on the market
  HOW TO USE:
  under connect method, add your subscribe channels.
  under messageReceived (callback method) add actions to be done when a msg is received.
  to publish, call client.publish(topic,msg)
  in loop take care of using non-blocking method or it will corrupt.
  Alberto Perro & DG - Officine Innesto 2019

  Updated to be the minimal parsing example to to control
  the Arduino behaviour throughout a json string sent to topic #hello

  The payload can be either

  {
    "name": "LED",
    "status": "open",
    "pin": 1,
    "color": "red"
  }

  or

  {
    "name": "LED",
    "status": "closed",
    "pin": 0,
    "color": "red"
  }


*/
#define BROKER_IP    "192.168.1.0"
#define DEV_NAME     "mqttdevice"
#define MQTT_USER    "user"
#define MQTT_PW      "password"
const char ssid[] = "wifi_ssid";
const char pass[] = "wifi_password";
#include <MQTT.h>
#ifdef ARDUINO_SAMD_MKRWIFI1010
#include <WiFiNINA.h>
#elif ARDUINO_SAMD_MKR1000
#include <WiFi101.h>
#elif ESP8266
#include <ESP8266WiFi.h>
#else
#error unknown board
#endif
WiFiClient net;
MQTTClient client;
unsigned long lastMillis = 0;

#include <Arduino_JSON.h>

void connect() {
  Serial.print("checking wifi...");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
    delay(1000);
  }
  Serial.print("\nconnecting...");
  while (!client.connect(DEV_NAME, MQTT_USER, MQTT_PW)) {
    Serial.print(".");
    delay(1000);
  }
  Serial.println("\nconnected!");
  client.subscribe("/hello"); //SUBSCRIBE TO TOPIC /hello
}

void messageReceived(String &topic, String &payload) {
  Serial.println("incoming: " + topic + " - " + payload);
  JSONVar myObject = JSON.parse(payload);
  //Serial.println(JSON.typeof(myObject));

  if (myObject.hasOwnProperty("name")) {
    Serial.print("myObject[\"name\"] = ");

    Serial.println((const char*) myObject["name"]);
  }

  if (myObject.hasOwnProperty("status")) {
    Serial.print("myObject[\"status\"] = ");

    Serial.println((const char*) myObject["status"]);
    //   Serial.println(myObject["status"]);

  }

  if (myObject.hasOwnProperty("pin")) {
    Serial.print("myObject[\"pin\"] = ");

    Serial.println((int) myObject["pin"]);
  }

  if (myObject.hasOwnProperty("color")) {
    Serial.print("myObject[\"color\"] = ");

    Serial.println((const char*) myObject["color"]);
  }

  if (topic == "/hello") {
    if (String((const char*)myObject["status"]) == "open") {
      
      Serial.println("open");
      digitalWrite(LED_BUILTIN, HIGH);
      
    } else if (String((const char*)myObject["status"]) == "closed") {

      Serial.println("closed");
      digitalWrite(LED_BUILTIN, LOW);
 
    }


    if ((int) myObject["pin"] == 1) {

      Serial.println("open");
      digitalWrite(LED_BUILTIN, HIGH);

    } else if ((int) myObject["pin"] == 0) {
 
      Serial.println("closed");
      digitalWrite(LED_BUILTIN, LOW);

    }

  }
}

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, pass);
  pinMode(LED_BUILTIN, OUTPUT);

  // Note: Local domain names (e.g. "Computer.local" on OSX) are not supported by Arduino.
  // You need to set the IP address directly.
  //
  // MQTT brokers usually use port 8883 for secure connections.
  client.begin(BROKER_IP, 1883, net);
  client.onMessage(messageReceived);
  connect();
}
void loop() {
  client.loop();
  if (!client.connected()) {
    connect();
  }
  // publish a message roughly every second.
  if (millis() - lastMillis > 1000) {
    lastMillis = millis();
    //  client.publish("/hello", "world"); //PUBLISH TO TOPIC /hello MSG world
  }
}

Minimal Json communication via MQTT and Node-RED

Credits

Davide Gomba
11 projects • 89 followers
Davide Gomba is an Italian maker / storyteller. Loves creating experiences about IoT STEAM Domotics Agrotech and Transformational Festival.
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Related channels and tags
  • Adafruit
  • Arduino
  • MQTT
  • Node-RED