Error while attaching a device to a gateway in IoT Central

Question

Here are the steps I did:
1- I created an IoT Device template with some telemetry.
2- I created an IoT Edge device template with downstream devices with a relationship to the device defined in 1).
3- I created an instance of the device defined in 1).
4- I created an instance of the gateway defined in 2).
5- I tried to attach the device created in 3) to the gateway created in 4) and I get the following message:
"Invalid relationship for instanceof dtmi:modelDefinition:b1o7aiopn2:v2 between devices XXX and YYY with relationship Type undefined!
Error code: 400.390.006.023 / e1mnn1s5xl.6

Could anyone tell me what I did wrong?

I also have a technical question if I eventually manage to make this work: Is it possible to access the list of attached devices from an IoT Edge module code?

Answer 1

Hello @Cédric Melançon ,

I'm not sure what the problem related to the error message.

Did you miss some sort of relationship Type setting?

Regarding:

I also have a technical question if I eventually manage to make this work: Is it possible to access the list of attached devices from an IoT Edge module code?

An IoT Edge module is sandboxed, it has no direct knowledge about child devices.

There are two options to work around this:

1. You could provide a list of child devices to the module using eg. Module Twin desired properties (which are persisted in the Module Twin) or a DirectMethod (not persisted)
2. Your module can build up a list over time while messages from child devices flow through the module (you have to check the 'var connectionDeviceId = message.ConnectionDeviceId' property for messages coming from child devices).

Answer 2

@Cédric Melançon

For the error, please ensure that you're sending the correct request body as part of the attestation flow, or use a device SDK.

Also, I suggest you, please check the documentations Define a new IoT gateway device type in your Azure IoT Central application and Add an Azure IoT Edge device to your Azure IoT Central application for step-by-step guidance on adding the device to IoT Central.

Do let us know if you have any further queries.

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