IoT Hub

Do the Azure setup first.

Devices registered in IoT Hub send readings with their own credentials. A message route forwards them to the event hub from Event Hubs, so the rest is the same. IoT Hub also has a built-in endpoint that Functions can read directly, but only with a connection string; routing to your own event hub keeps managed identities throughout. Set up Event Hubs first. Registering real devices is covered in the IoT Hub docs.

export HUB=timelake-$RANDOM
az iot hub create -g $RG -n $HUB --sku S1
az iot hub identity assign -g $RG -n $HUB --system-assigned \
  --role "Azure Event Hubs Data Sender" --scopes $EH_SCOPE
az iot hub message-endpoint create eventhub -g $RG -n $HUB --en readings \
  --endpoint-uri sb://$EH_NAMESPACE.servicebus.windows.net --entity-path readings --identity '[system]'
az iot hub message-route create -g $RG -n $HUB --route-name readings --endpoint-name readings \
  --source devicemessages

The message-endpoint and message-route commands come with the azure-iot CLI extension, which installs on first use. The free tier (--sku F1, 8,000 messages a day, one per subscription) works for trying it.

Try it, sending as a registered device:

az iot hub device-identity create -n $HUB -d pump-1
az iot device send-d2c-message -n $HUB -d pump-1 \
  --data '{"time": "2026-01-05T10:15:00Z", "device_id": "pump-1", "temp": 64.0, "humidity": 40}'

Include device_id in each message, as above. IoT Hub also stamps every message with the sending device's id (iothub-connection-device-id).