page_type	languages	products	name	description	urlFragment
sample	csharp nodejs	dotnet-core azure azure-iot azure-iot-dps azure-iot-hub azure-digital-twins azure-functions azure-event-hubs vs-code	Azure Digital Twins and IoT Hub provisioning integration sample	A code sample to use the Device Provisioning Service and IoT Hub to automatically create and remove devices in Azure Digital Twins.	adt-iothub-provision-sample

Azure Digital Twin and IoT Hub provisioning integration sample

This is a sample project to show possible patterns for the automatic integration of the new Azure Digital Twins and IoT Hub. The following scenarios are implemented:

• An Azure Device Provisioning Service (DPS) custom allocation Azure Function to look up details for a device in Azure Digital Twins and inform the provisioning process.
• A simulated device device that sends the necessary information to DPS for the allocation decision.
• An Azure Function that maps device telemetry to the ADT twin instance and updates a property on the twin (a Temperature Property).
• An Azure Function that implements the automatic deletion of an Azure Digital Twin entity when the linked device is deleted in IoT Hub.
• Two Event Hubs for the telemetry messages and device lifecycle events to automatically interact with ADT.

How to use this sample

• Set up an Azure Digital Twin Service using the documentation.
• Use the Azure Digital Twins Explorer to upload the SpaceModel.json and ThermostatModel.json found under the folder /models. Through the Explorer tool, create a parent and a few chidren Thermostat objects. In the twins of type Thermostat you will see a property HubRegistrationId. This property can be used on one of the twins to reflect the RegistrationId that you will be using in DPS and automatically assigning the device to a twin.
• Create an IoT Hub, Device Provisioning Service and an Azure Functions service.
• Create an Event Hubs namespace and two event hubs.
  • lifecycleevents
  • deviceevents
• Create a consumer group in each event hub.
• Create two endpoints in Azure IoT Hub: pointing to each of the Event Hubs.
• Create a Route for Device Messages to the deviceevents endpoint.
• Create a Route for Device Lifecycle Events to the lifecycleevents endpoint.
• Download and install Visual Studio Code and the following extensions:
  • Azure IoT Tools
  • Azuer Functions
• Clone this repo
  • cd functions
  • dotnet restore
• Deploy the application to your Azure Functions. Set the following configuration app settings:
  • ADT_SERVICE_URL
  • EVENTHUB_CONNECTIONSTRING
• Create a Group Enrollment in DPS and link to the DpsAdtAllocationFunc in your functions instance.
• Customise the device simulator .env file with the credentials for your DPS Scope.
• Customise and run the device-simulator code:
  • Rename .env.template to .env.
  • Set the variables:
    • PROVISIONING_IDSCOPE to the scope of your DPS
    • PROVISIONING_REGISTRATION_ID to your registration ID, if you assigned one or specificy something unique
    • ADT_MODEL_ID set this to dtmi:contosocom:DigitalTwins:Thermostat;2
    • PROVISIONING_SYMMETRIC_KEY to your DPS enrollment master key, the script calculates a derived key. Note this is for testing only, we never recommend having the master key on the device.
• Restore the packages and run the device simulator code
  • npm install
  • node .\adt_custom_register.js [registrationId]
• Use the Azure Digital Twins Explorer to view the registered devices.

Key Concepts

The integration flow between IoT Hub, DPS and Azure Digital Twins is the following:

Let's go through each of the steps.

Note: we assume Azure Digital Twins has been setup with the models supplied in this repo (see folder /models).

1. Device is using Azure IoT SDK to connect to DPS for getting itself provisioned in IoT Hub. Within the DPS request, it sets a custom payload which includes the ADT Model ID.
2. DPS enrollment group is setup with a custom allocation policy (Azure Function).

{
    "enrollmentGroup": {
        "enrollmentGroupId": "test1",
        ...
    },
    "deviceRuntimeContext": {
        "registrationId": "deviceid_reg",
        "symmetricKey": {},
        "payload": {
            "modelId": "dtmi:contosocom:DigitalTwins:Thermostat;2"
        }
    },
    "linkedHubs": [
        "HUB_NAME.azure-devices.net"
    ]
}

3. The custom allocation policy uses the modelId from the custom payload, along with the RegistrationId to query ADT:

• If a Twin instance with the supplied RegistrationId exists, then it simply returns its ID to the function.
• If not, the function creates it and returns its ID to the function. The function returns custom Device Twin to DPS for initializing the device.

"tags": {
  "dtId": "the_twin_instance_id",
  "dtmi": "dtmi:contosocom:DigitalTwins:Thermostat;2"
},

4. DPS uses the information from the custom allocation function to provision the device in the right IoT Hub, along with custom Device Twin Tags.
5. Device gets the assigned hub and connects.
6. Device uses IoT Hub SDK to send telemetry to the assigned IoT Hub.
7. In IoT Hub, a Route is setup to send the Telemetry messages to an Event Hub, while adding Message Enrichments.
8. Azure Function DeviceTelemetryToTwinFunc consumes from the Event Hub, picks up each message and updates the Twin instance Id in ADT. For this example, we update the `Temperature' Property in the Twin.
9. A manual action can be taken to delete the Device from IoT Hub.
10. In this case, we also want to delete the Twin instance for that device in ADT. To do this we create a Route in IoT Hub to send all 'Lifecycle events' to another Event Hub. Function DeleteDeviceInTwinFunc consumes the event hub.
11. If the operation is of type deleteDeviceIdentity, we use ADT API to find the Twin instance to be deleted.