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Enable BeagleBone Black connection to AirVantage using MQTT

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David Sciamma edited this page Apr 16, 2014 · 1 revision

This article explains the different steps to enable AirVantage connection for BeagleBoneBlack using MQTT.

Prerequisite

  • Have a basic knownlege of MQTT. See the other tutorial about MQTT for airvantage: MQTT API.
  • Have a basic knownlege of NodeJS.
  • Have a BeagleBone Black setup with an Ångström distribution with an Internet access.

Setup Hardware

Step 1. Plug the BeagleBone Black to USB.

Step 2. Set up Internet on your device with an ethernet cable.

Step 3. Go to the Cloud9 IDE by openning the following url in a browser: http://192.168.7.2:3000/. Where 192.168.7.2 is the default IP of the BeagleBone.

Step 4. Create a new file in the workspace.

Application Model

The procedure to create an application model is decribed in the MQTT Tutorial, we need this application package to continue.

Retreive the name and the password of your beaglebone

Open a browser to this url: http://192.168.7.2/Support/BoneScript/getPlatform/. Click on the run button. Take note of the serial number and the name, we will use it for the next step.

Register your system

The registrtration procedure is decribed in the MQTT Tutorial, follow theses steps and use previously noted serial-number and name of the BeagleBone to create a system for your device.

Send and Receive data

Open the created file to start coding an example using the following snippets.

Intialize the MQTT channel:

At first, we need to create a MQTT client instance with the right congfiguration.

var mqtt = require('mqtt');

var port = 1883;
var server = "tcp://na.airvantage.net";

var serialnumber = "3713BBBK7777"; //serialnumber
var password = "1234";

var mqtt_options = {clientId: serialnumber, username: serialnumber, password: password};

var client = mqtt.createClient(port, server, mqtt_options);

console.log("Client started");

With same serialnumber and password used for system creation on AirVantage.

Send data to Airvantage

We will send three temperature values and one threshold value. The variables string identifier machine.temperature and machine.threshold are the same as definied in your system application model.

//Send values
console.log("Sending value");

//Publish a message on the right topic
client.publish(serialnumber+'/messages/json',JSON.stringify([
  {
    "machine.temperature": [{
      "timestamp" : new Date().getTime(), 
      "value" : "42.2"
    },
    {
      "timestamp" : new Date().getTime(), 
      "value" : "24.5"
    },
    {
      "timestamp" : new Date().getTime(), 
      "value" : "42.9"
    }]
  },
  {
    "machine.threshold": [{
      "timestamp" : new Date().getTime(), 
      "value" : "30"
    }]
  }
]));

Receive messages

This snippet handles two different messages sent by AirVantage. The first message contains an updated value of the threshold setting. The second message contains a request from AirVantage to get current temperature.

console.log("Waiting for task");

//wait for a incoming message
client.on('message', function (topic,message){

      var data = JSON.parse(message);

      //receiving a new threshold value
      if ("write" in data[0] && data[0].write[0] === "machine.threshold") {
          console.log("new threshold received: " + data[0].write[0]["machine.threshold"]);          
      }
      
      //receiving a request to send back the current temperature
      if ("read" in data[0] && data[0].read[0] === "machine.temperature") {
          console.log("AirVantage is asking for the last temperature");
          
	  //publish on the right topic the current temperature
          client.publish(serialnumber+'/messages/json',JSON.stringify([
              {
                "machine.temperature": [{
                  "timestamp" : new Date().getTime(), 
                  "value" : 12 //quite cold indeed
               }]
            }]
          ));
      }
});

Going forward, send an IO.

The following snippet send an IO value every 5 seconds.

//Send an IO
var b = require('bonescript');

//function to send a value
function sendValue(x) {
    console.log("Sending P8_19 value: "+ x.value);
    if ( x.err !== null) {
        client.publish(serialnumber+'/messages/json',JSON.stringify([
            {
                "machine.P8_19": [{
                    "timestamp" : new Date().getTime(), 
                    "value" : x.value
                }]
            }
        ]));
    } else {
        console.log("Error while retriving pin P8_19 value: "+ x.err);
    }
}

//set pin as Input
b.pinMode('P8_19', b.INPUT);

//get a pin value and send it every 5s
setInterval( function(){
    b.digitalRead('P8_19', sendValue);
}, 5000);

Testing

Here are some hints to be test your code using AirVantange webUI.

See communications received by Airvantage

On AirVantage data are stored by system. So you need find your system in the Monitor activity and consult its timeline from its details page.

Send a value to the device

To send a value, you need to have declared a setting in the application model associated to your system. Then you can edit it by following some steps:

Step 1. Find your system in the Monitor activity and open its detail page.

Step 2. Go to the detail page of the application containing the setting you want to modify. Here you can see the values sent by the BeagleBone.

Step 3. To modify a value, click on the Edit button.

Step 4. Modify the value and click on Apply. An operation is created to perform the task. Go back to the system details page to monitor all system operations.

Request the device to send back a value

The mechanism enabling to request values from a device using Airvantage works throught Report. So first, you need to create a report. Then from the Monitor activity, on your system detail, you will be able to launch a retrieve data operation.

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