Azure Digital Twins demos

Updates From Event Hub to Azure Digital Twins

sequenceDiagram
    Note right of On-premises App: See JSON<br/>payload below
    On-premises App->>+Event Hub: Send event
    Azure Functions-->>+Event Hub: Receive event
    Note right of Azure Functions: Map fields from<br/>payload to digital<br/>twin model definitions
    Azure Functions->>Azure Digital Twins: Update digital twin

Using static structure

You can find example models in car-demo folder for Car and Tyre.

Example payloads if ProcessingLogic is set to ByID:

{
  "_id": "Matiz",
  "carStatus": "Moving",
  "speed": 121.8
}

{
  "_id": "LeftFront",
  "tyreStatus": "OK",
  "pressure": 2.3
}

Note: _id is identifier of the digital twin.

These payloads are picked by AzureDigitalTwinsUpdaterFunc which then processes mapping of incoming data to the target digital twin.

Note: Only Property types in the model are updated by the updater.

You can send events to Event Hub using examples.ps1 script.

Example search in Azure Digital Twin Explorer to find all these twins:

SELECT * FROM digitaltwins WHERE STARTSWITH($metadata.$model, 'dtmi:com:janneexample')

Using dynamic structure

You can find example models in ISA95 folder for OPCUANodeset and OPCUANodeInteger. Using these models, you can create dynamic structure to represent values in child twins.

Example payloads if ProcessingLogic is set to ByChild:

{
  "_id": "myeq123",
  "MyValue1": 8,
  "MyValue2": 12
}

SELECT T, CT FROM digitaltwins T JOIN CT RELATED T.contains WHERE T.$dtId = '50001'

Deployment to Azure

Key deployment steps:

Create Azure Digital Twin
- Load example models into it from car-demo
Create Event Hub namespace
- Create adt Event Hub and copy connection string
Create Azure Functions App
- App Settings to Function App
  - ADTOptions__ADTInstanceUrl e.g., https://<your-adt-instance>.api.neu.digitaltwins.azure.net/
  - ADTOptions__IDFieldName e.g., _id
  - ADTOptions__ProcessingLogic either ByID or ByChild
    - ByID searches by digital twin id $dtId. Found twin is directly updated.
    - ByChild searches parent digital twin by equipmentID, finds all children twins by ID and updates child twins OPCUANodeValue property.
  - EventHubName e.g., adt
  - EventHubConnectionString e.g., Endpoint=sb://<your-eventhub-instance>.servicebus.windows.net/;SharedAccessKeyName=...
- Enable System Assigned Managed Identity
Add Role Assignment: Azure Digital Twins Data Owner role to the managed identity of Azure Functions App
Deploy using Visual Studio to Azure Functions app
- Visual Studio will validate that settings in Azure Function App are correct e.g., FUNCTIONS_WORKER_RUNTIME=dotnet-isolated and FUNCTIONS_EXTENSION_VERSION=~4

Links

Azure Digital Twins getting started samples

Azure Digital Twins APIs and SDKs