#AzureIoT – Working with Digital Twin Settings on an Azure IoT Edge Module

Hi !

In my previous series of posts I wrote about how to create custom modules to work using Custom Vision projects, and also sensors in a Raspberry Pi. Today, I’ll pick my Door demo, and share some insights about how to work work with Twin properties.

Define Twin Properties

Let’s start defining our twin properties. We can do this in our Visual Studio project, adding the information to the [deployment.template.json] file. Or, we can also do this on the module definition, on the Azure IoT Portal.

Once we are setting the module properties, we can add the necessary information in the [Module Twin Settings] tab.

azure iot define twin properties for custom iot edge module

Once the module is success fully deployed, we can access to the twin properties and check the desired and reported states.

azure iot twin properties as part of the module

Reading Digital Twin properties changes

Now it’s time to create a new thread.. In this thread, we will check for changes in the Digital Twin properties and work with those changes. The following code is based on the references suggested code.

Code will iterate and check the DT changes every N seconds
When changes are received, the code will get specific values for door state and door state description

	def twin_patch_receive_messages():
	global twin_callbacks
	global module_client
	global read_twin_sleep_interval

	# Define behavior for receiving twin desired property patches
	def twin_patch_handler(twin_patch):
	try:
	# sample received data
	# {'doorState': 1, 'doorStateDesc': '3', 'doorStateSource': 'digital twin new', '$version': 88}
	doorState = twin_patch["doorState"]
	source = twin_patch["doorStateSource"]
	print (f" New Door state : {doorState} – source : {source}")

	except Exception as ex:
	print ( "Unexpected error in twin_patch_handler: %s" % ex )

	while True:
	try:
	# Set handlers on the client
	module_client.on_twin_desired_properties_patch_received = twin_patch_handler
	twin_callbacks += 1
	time.sleep(read_twin_sleep_interval) # settings to define how often refresh dt information

	except Exception as ex:
	print ( "Unexpected error in twin_patch_listener: %s" % ex )

view raw readDigitalTwinInformationInAzIotEdgeModule.py hosted with ❤ by GitHub

The printed log is similar to the following sample:

2021-09-08 20:51:10.836744 | Twin patch received - loops : 23
2021-09-08 20:51:10.837610 | {'doorState': 0, 'doorStateDesc': '', 'doorStateSource': 'digital twin', '$version': 89}
2021-09-08 20:51:10.837690 |  New Door state : 0 - source : digital twin
2021-09-08 20:51:10.837727 | start close - source digital twin
2021-09-08 20:51:12.240233 | start send message

Updating Twin properties

In order to update twin properties, we can use the following code as reference.

	def update_device_state(results, source, doorState, doorStateDesc):
	global module_client
	try:
	# update twin properties
	reported_patch = {"doorState": doorState}
	asyncio.run(module_client.patch_twin_reported_properties(reported_patch))
	reported_patch = {"doorStateDesc": doorStateDesc}
	asyncio.run(module_client.patch_twin_reported_properties(reported_patch))
	reported_patch = {"doorStateSource": source}
	asyncio.run(module_client.patch_twin_reported_properties(reported_patch))

	except Exception as e:
	AzureIoTLogger.Log ( "update_device_state – Unexpected error %s " % e )
	raise

view raw updateDigitalTwinPropertiesinAzIoTEdgeModule.py hosted with ❤ by GitHub

On the Module definition, we can check the reported properties.

azure iot updated and reported properties on azure iot edge module

References

Happy coding!

Greetings

El Bruno

Azure ☁ IoT

Create an Azure IoT Module using Raspberry Pi and Grove Sensors

Create an Azure IoT Module from Azure Custom Vision project

Create and export a Custom Vision Project as Docker image
Analyze the content of the CV Docker image
Create and analyze an Azure IoT Module
Merge the CV project as an Azure IoT Module
Deploy to an Azure IoT device and test the CV module
Send telemetry for each analyzed image
Add digital twin configuration to the Azure IoT module (coming soon)

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Define Twin Properties

Reading Digital Twin properties changes

Updating Twin properties

References

Azure ☁ IoT

Create an Azure IoT Module using Raspberry Pi and Grove Sensors

Create an Azure IoT Module from Azure Custom Vision project

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