Control Your IoT Cloud Kit via MQTT and Node-RED
Components and Supplies
Apps and Online Services
About This Project
We are going to make our MKR IoT Bundle connect to a local server (this very same technology could be hosted on AWS or wherever).
The connection is going to be held through MQTT, a lightweight message protocol developed for machine to machine communication.
In order to do this we need to do some work on the server side. I'm using a Raspberry PI with Node-RED on it, but you can host an instance of Node-RED on Windows/MAC/Linux or on the Cloud (Bluemix, AWS, etc..).
This tutorial heavily relies on Interfacing Arduino MKR or ESP via MQTT - Node-RED 101 we did back in January. We are touching all the points and adding the data visualisation, but don't hesitate to go through that tutorial in order to see all the steps in the setup of the cloud instance.
The Server
In order to prepare your Node-RED instance properly you need to install two Nodes: Node-RED Dashboard and an MQTT brocker written in node.js.
Once you are done, copy the flow you find in the sowftare section in your palette by doing import > clipboard
The Client
We are using the Iot Prime MKR Bundle to visualise Light, Humidity, Pressure and Temperature using MQTT. We are going to create a channel for each one of this data, as well as the two relays.
We'll be using the MQTT Library by Joƫl GƤhwiler 256dpi (you should be able to run everything from your Arduino Online Editor sketch, bu adding Wifi information to have the board conneting to the internet.
Don't forget the MKR_ENV Library you need to use the data from the board (if going with the online IDE, it's going to be impoted automatically š
The sending of the data is done in loop:
1// read enrivornmental data2 float t = ENV.readTemperature();3 float h = ENV.readHumidity();4 float p = ENV.readPressure();5 float l = ENV.readLux();and later published, casted ina a
string()1if (millis() - lastMillis > 1000) {2 lastMillis = millis();3 client.publish("/hello", "world"); 4 client.publish("/temp", String(t)); 5 client.publish("/humidity", String(h)); 6 client.publish("/pressure", String(p)); 7 client.publish("/light", String(l)); 8 }In order to read the value of the pushbutton of the Node-RED Dashboard, I've nested two condition inside of the
messageReceivedIf the topic is
/relay1relay21void messageReceived(String &topic, String &payload) {2 Serial.println("incoming: " + topic + " - " + payload);3 if (topic == "/relay1") {4 if (payload == "true") {5 digitalWrite(R1, HIGH);6 digitalWrite(led, HIGH);7 } else if (payload == "false") {8 digitalWrite(R1, LOW);9 digitalWrite(led, LOW);10 }11 }12 if (topic == "/relay2") {13 if (payload == "true") {14 digitalWrite(R2, HIGH);15 digitalWrite(led, HIGH);16 } else if (payload == "false") {17 digitalWrite(R2, LOW);18 digitalWrite(led, LOW);19 }20 }21}You can
#copypastaJSON
Node-Red Dashboard Flow
This flow is visualizing the data sent via MQTT to the brocker.
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