Balaji Barmavat
Published © GPL3+

Azure Blink LED App

A simple blinking LED (device to cloud and cloud to device) application based on Raspberry Pi 3 and Microsoft Azure.

EasyWork in progress4 hours1,117
Azure Blink LED App

Things used in this project

Hardware components

Raspberry Pi 3 Model B
Raspberry Pi 3 Model B
×1
Breadboard (generic)
Breadboard (generic)
×1
LED (generic)
LED (generic)
×1
Resistor 221 ohm
Resistor 221 ohm
×1

Software apps and online services

Microsoft Azure
Microsoft Azure

Story

Read more

Schematics

Circuit diagram

Connect LED, wires and resistor
Img 1273 ytk7lmxykv

Code

Blinking LED Node JS

JavaScript
Blinking LED Node JS
/*
* IoT Hub Raspberry Pi NodeJS 
*/
'use strict';

var wpi = require('wiring-pi');

// GPIO pin of the LED
var CONFIG_PIN = 7;
// Blink interval in ms
var INTERVAL = 2000;
// Total blink times
var MAX_BLINK_TIMES = 20;

wpi.setup('wpi');
wpi.pinMode(CONFIG_PIN, wpi.OUTPUT);

var blinkTimes = 0;
/**
 * Blink LED and log information to console.
 */
function blinkLED() {
  // Terminate process after blinking LED for max allowed times
  if (blinkTimes >= MAX_BLINK_TIMES) {
    process.exit(0);
  }

  blinkTimes++;
  console.log("[Device] #" + blinkTimes + " Blink LED \n");

  // Light up LED for 100 ms
  wpi.digitalWrite(CONFIG_PIN, 1);
  setTimeout(function () {
    wpi.digitalWrite(CONFIG_PIN, 0);
  }, 100);
}

// Blink LED every other INTERVAL time
setInterval(blinkLED, INTERVAL);

Send Msg to Azure IoT

JavaScript
Send Message to IoT
App.js
/*
* IoT Hub Raspberry Pi NodeJS - 
*/
'use strict';

var wpi = require('wiring-pi');
var Message = require('azure-iot-device').Message;
// Use AMQP client to communicate with IoT Hub
var clientFromConnectionString = require('azure-iot-device-amqp').clientFromConnectionString;

// Get device id from IoT device connection string
function getDeviceId(connectionString) {
  var elements = connectionString.split(';');
  var dict = {};
  for (var i = 0; i < elements.length; i++) {
    var kvp = elements[i].split('=');
    dict[kvp[0]] = kvp[1];
  }
  return dict.DeviceId;
}

// Read device connection string from command line arguments
var iotDeviceConnectionString = process.argv[2];
var deviceId = getDeviceId(iotDeviceConnectionString);

// GPIO pin of the LED
var CONFIG_PIN = 7;
// Blink interval in ms
var INTERVAL = 2000;
// Total messages to be sent
var MAX_MESSAGE_COUNT = 20;
var sentMessageCount = 0;

wpi.setup('wpi');
wpi.pinMode(CONFIG_PIN, wpi.OUTPUT);

/**
 * Start sending messages after getting connected to IoT Hub.
 * If there is any error, log the error message to console.
 * @param {string}  err - connection error
 */
function connectCallback(err) {
  if (err) {
    console.log('[Device] Could not connect: ' + err);
  } else {
    console.log('[Device] Client connected\n');
    // Wait for 5 seconds so that host machine gets connected to IoT Hub for receiving message.
    setTimeout(sendMessage, 5000);
  }
}

/**
 * Blink LED.
 */
function blinkLED() {
  // Light up LED for 100 ms
  wpi.digitalWrite(CONFIG_PIN, 1);
  setTimeout(function () {
    wpi.digitalWrite(CONFIG_PIN, 0);
  }, 100);
}

/**
 * Construct device-to-cloud message and send it to IoT Hub.
 */
function sendMessage() {
  sentMessageCount++;
  var message = new Message(JSON.stringify({ deviceId: deviceId, messageId: sentMessageCount }));
  console.log("[Device] Sending message #" + sentMessageCount + ": " + message.getData());
  client.sendEvent(message, sendMessageCallback);
}

/**
 * Blink LED after message is sent out successfully, otherwise log the error message to console.
 * If sent message count is less than max message count allowed, schedule to send another message.
 * Else, exit process after several seconds.
 * @param {object}  err - sending message error
 */
function sendMessageCallback(err) {
  if (err) {
    console.log('[Device] Message error: ' + err.toString());
  } else {
    // Blink once after successfully sending one message.
    blinkLED();
  }

  if (sentMessageCount < MAX_MESSAGE_COUNT) {
    setTimeout(sendMessage, INTERVAL);
  } else {
    // Wait 5 more seconds to exit so that Azure function has the chance to process sent messages.
    setTimeout(function () {
      process.exit();
    }, 5000);
  }
}

// Construct IoT Hub device client and connect to IoT Hub.
var client = clientFromConnectionString(iotDeviceConnectionString);
client.open(connectCallback);

Credits

Balaji Barmavat

Balaji Barmavat

1 project • 3 followers
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