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Simple temperature alert with Azure IoT Hub and an mbed board

autor: Olivier Bloch
Ostatnia aktualizacja: 2016-11-14
Współautorzy:
Edytuj w witrynie GitHub

Simple IoT project using Azure IoT Hub and an mbed device sending telemetry data. IoT Hub is used to ingest data from the device, and to notify the devie when alerts are triggered by Cloud services. To learn more about Azure IoT Hub, check out the Azure IoT Dev center.

Running this sample

Hardware prerequisites

In order to run this sample you will need the following hardware: - mbed-enabled Freescale FRDM-K64F - mbed Application shield - Both can be found together in the mbed Ethernet IoT Started Kit

Software prerequisites

Services setup

In order to run the sample you will need to do the following: - Create an IoT hub that will receive data from devices and send commands back to it - Create an Event hub into which we will post alerts - Create a Stream Analytics job that will read data from the IoT hub and post alerts into the Event hub - Create a Storage account that will be used by the worker role - Deploy a simple worker role that will read alerts from the Event hub and forward alerts to devices through the IoT hub

Create an IoT Hub

  1. Log on to the Azure Portal.

  2. In the jumpbar, click New, then click Internet of Things, and then click IoT Hub.

  3. In the New IoT Hub blade, specify the desired configuration for the IoT Hub.

    • In the Name box, enter a name to identify your IoT hub. When the Name is validated, a green check mark appears in the Name box.
    • Change the Pricing and scale tier as desired. This tutorial does not require a specific tier.
    • In the Resource group box, create a new resource group, or select and existing one. For more information, see Using resource groups to manage your Azure resources.
    • Use Location to specify the geographic location in which to host your IoT hub.
  4. Once the new IoT hub options are configured, click Create. It can take a few minutes for the IoT hub to be created. To check the status, you can monitor the progress on the Startboard. Or, you can monitor your progress from the Notifications section.

  5. After the IoT hub has been created successfully, open the blade of the new IoT hub, take note of the Hostname, and select the Key icon on the top.

  6. Select the Shared access policy called iothubowner, then copy and take note of the connection string on the right blade. Also take note of the Primary key

Your IoT hub is now created, and you have the Hostname and connection string you need to complete this tutorial.

For the creation of the Stream Analytics job Input, you will need to retreive some informations from the IoT Hub: - From the Messaging blade (found in the settings blade), write down the Event Hub-compatible name - Look at the Event-hub-compatible Endpoint, and write down this part: sb://thispart.servicebus.windows.net/ we will call this one the IoTHub EventHub-compatible namespace - For the key, you will need the Primary Key read in step #6

Create an Event Hub

  1. Log on to the Azure Management Portal.

  2. In the lower left corner of the page, click on the + NEW button.

  3. Select App Services, Service Bus, Event Hub, Quick Create

  4. Enter the following settings for the Event Hub (use a name of your choice for the event hub and the namespace):

    • Event Hub Name: "myeventhubname"
    • Region: your choice
    • Subscription: your choice
    • Namespace Name: "mynamespacename-ns"
  5. Click on Create Event Hub

  6. Select the mynamespacename-ns and go in the Event Hub tab

  7. Select the myeventhubname event hub and go in the Configure tab

  8. in the Shared Access Policies section, add a new policy:

    • Name = "readwrite"
    • Permissions = Send, Listen
  9. Click Save, then go to the evnet hub Dashboard tab and click on Connection Information at the bottom

  10. Write down the connection string for the readwrite policy name.

Create a Stream Analytics job

  1. Log on to the Azure Portal.

  2. In the jumpbar, click New, then click Internet of Things, and then click Stream Analytics Jobs.

  3. Enter a name for the job, choose your subscription, select the same resource group you created when creating the IoT Hub, Select the location, and click on Create.

  4. Once the job is created, click on the Inputs tile in the job topology section. In the Inputs blade, click on Add

  5. Enter the following settings:

    • Input Alias = "tempsensors"
    • Type = "Data Stream"
    • Source = "IoT Hub"
    • IoT Hub = "myiothubname" (use the name for the IoT Hub you create before)
    • Shared Access Policy Name = "iothubowner"
    • Shared Access Policy Key = "iothubowner Primary Key" (That's the key you wrote down when creating the IoT Hub)
    • IoT Hub Consumer Group = "" (leave it to the default empty value)
    • Event serialization format = "JSON"
    • Encoding = "UTF-8"
  6. Back to the Stream Analytics Job blade, click on the Query tile. In the Query settings blade, type in the below query and click Save

  SELECT
      System.timestamp AS timestart,
      ObjectName AS dsplalert,
      ObjectType AS alerttype,
      Version AS message,
      TargetAlarmDevice AS targetalarmdevice
  INTO
      eventhub
  FROM
      tempsensors
  WHERE temp>82
  1. Back to the Stream Analytics Job blade, click on the Outputs tile and in the Outputs blade, click on Add

  2. Enter the following settings then click on create:

    • Output Alias = "eventhub"
    • Source = "Event Hub"
    • Service Bus Namespace = "mynamespacename-ns
    • Event Hub Name = "myeventhubname"
    • Event Hub Policy Name = "readwrite"
    • Event Hub Policy Key = "Primary Key for readwrite Policy name" (That's the one you wrote down after creating the event hub)
    • Partition Key Column = "4"
    • Event Serialization format = "JSON"
    • Encoding = "UTF-8"
    • Format = "Line separated"
  3. Back in the Stream Analytics blade, start the job by clicking on the Start button at the top

Create a storage account

  1. Log on to the Azure Portal.

  2. In the jumpbar, click New and select Data + Storage then Storage Account

  3. Choose Classic for the deployment model and click on create

  4. Enter the name of your choice (i.e. "mystorageaccountname" for the account name and select your resource group, subscription,... then click on "Create"

  5. Once the account is created, find it in the resources blade and write down the primary connection string for it to configure the worker role

Deploy the worker role

The sample uses a worker role to trigger alerts back on devices through IoT Hub. To build an deploy the worker role here are the few simple steps:

  1. Clone the repository on your machine (see the links on top of this tutorial)

  2. Open the solution events_to_device_service\events_to_device_service.sln in Visual Studio 2015

  3. open the file app.config and replace the fields below with the connection strings from the event hub, the storage account and the Iot Hub

    <add key="Microsoft.ServiceBus.ConnectionString" value="[EventHub Connection String]" />
    <add key="Microsoft.ServiceBus.EventHubName" value="[Event Hub Name]" />
    <add key="AzureStorage.AccountName" value="[Storage Account Name]" />
    <add key="AzureStorage.Key" value="[Storage Account Key]" />
    <add key="AzureIoTHub.ConnectionString" value="[IoT Hub Connection String]" />
    
  4. Compile the project and publish to Azure

Create a new device identity in the IoT Hub

To connect your device to the IoT Hub instance, you need to generate a unique identity and connection string. IoT Hub does that for you. To create a new device identity, you have the following options: - Use the Device Explorer tool (runs only on Windows for now) - Use the node.js tool - For this one, you need to have node installed on your machine (https://nodejs.org/en/) - Once node is installed, in a command shell, type the following commands:

```
npm install -g iothub-explorer
```
  • You can type the following to learn more about the tool

    iothub-explorer help
    
  • Type the following commands to create a new device identity (replace in the commands with the connection string for the iothubowner that you retreive previously in the portal.

    iothub-explorer <connectionstring> create mydevice --connection-string
    
  • This will create a new device identity in your IoT Hub and will display the required information. Copy the connectionString

Connect the device

  1. Connect the board to your network using an Ethernet cable. This step is required, as the sample depends on Internet access.

  2. Plug the device into your computer using a micro-USB cable. Be sure to attach the cable to the correct USB port on the device (the CMSIS-DAP USB one, see here to find which one it is).

  3. Follow the instructions on the mbed handbook to setup the serial connection with your device from your development machine. If you are on Windows, install the Windows serial port drivers located here.

Create mbed project and import the sample code

  1. In your web browser, go to the mbed.org developer site. If you haven't signed up, you will see an option to create a new account (it's free). Otherwise, log in with your account credentials. Then click on Compiler in the upper right-hand corner of the page. This should bring you to the Workspace Management interface.

  2. Make sure the hardware platform you're using appears in the upper right-hand corner of the window, or click the icon in the right-hand corner to select your hardware platform.

  3. Click Import on the main menu. Then click the Click here to import from URL link next to the mbed globe logo.

  4. In the popup window, enter the link for the sample code https://developer.mbed.org/users/AzureIoTClient/code/temp_sensor_anomaly/

  5. You can see in the mbed compiler that importing this project imported various libraries. Some are provided and maintained by the Azure IoT team (azureiot_common, iothub_client, iothub_http_transport, proton-c-mbed), while others are third party libraries available in the mbed libraries catalog.

  6. In the temp_sensor_anomaly\main.cpp file, find and replace values in the following lines of code with your device connection string (to obtain this device connection string you can use the node.js tool as described earlier in this tutorial or using device explorer as instructed here):

  static const char* connectionString = "[connection string]";
  static const char* deviceId = "[device ID]"; /*must match the one on connectionString*/
  1. Click Compile to build the program. You can safely ignore any warnings, but if the build generates errors, fix them before proceeding.

  2. If the build is successful, a .bin file with the name of your project is generated. Copy the .bin file to the device. Saving the .bin file to the device causes the current terminal session to the device to reset. When it reconnects, reset the terminal again manually, or start a new terminal. This enables the mbed device to reset and start executing the program.

  3. Connect to the device using an serial terminal client application, such as PuTTY. You can determine which serial port your device uses by checking the Windows Device Manager:

  4. In PuTTY, click the Serial connection type. The device most likely connects at 115200, so enter that value in the Speed box. Then click Open:

The program starts executing. You may have to reset the board (press CTRL+Break or press on the board's reset button) if the program does not start automatically when you connect.

Now your device is sending telemetry data to Azure through IoT Hub. The Stream Analytics job is doing near real time analytics on the device data and will post alerts based on the SQL request it is configured with. The Worker role will pick up the alerts generated by Stream Analytics and will forward the alerts to the device through IoT Hub. The device will start bleeping and will display the name of the device that triggered the alert. You can push data from several devices, provisionning them with several connection strings that you can generate as instructed above.

More information

To learn more about Azure IoT Hub check out the Azure IoT Dev center. In the IoT dev center you will also find plenty simple samples for connecting many sorts of devices to Azure IoT Hub. You can replace the mbed board in this sample with any of the supported devices by simply adapting the meta data and the format of the data sent to the services set up in this sample.