nRF9160: MQTT to Azure IoT Hub with SAS Token

[John M]

I am attempting to demonstrate connectivity from the nRF9160-DK to an Azure IoT Hub via SAS Token authentication.  My main reference was this tutorial from Microsoft:

https://learn.microsoft.com/en-us/azure/iot-develop/tutorial-use-mqtt

I was able to successfully follow this tutorial to demonstrate MQTT / SAS Token connectivity between a Raspberry Pi and my Azure IoT Hub.

I then wanted to demonstrate the same connectivity with the nRF9160-DK talking across the cellular network to my IoT Hub.  I started with the MQTT code example from Lesson 4 Exercise 2 of the of the Cellular IoT fundamental Dev Academy course:

https://academy.nordicsemi.com/topic/lesson-4-exercise-2/  

I added a new header file "azure_mqtt.h" with the same Azure device name, SAS Token, etc., as was used in the Raspberry PI IoT device.

I then modified the mqtt_connection.cpp file to use a username and password to log into the IoT hub, similar to what worked in the Raspberry Pi application:

The modified application built and flashed to the device correctly.  However, when the application runs, it gives the following error messages:

<err> nrf_modem: Modem error: 0x4, PC: 0xedffc

<wrn> modem_key_mgmt: Failed to retrieve CMEE status, err -1

<err> Lesson4_Exercise2: Failed to provision CA certificate: -1

I can see that this error is happening at the step where the code is provisioning the device certification, which is prior to connecting to the IoT hub.  How can I fix this?

[Øyvind]

Hello, 

We do not have support for Azure SAS token authentication in the nRF Connect SDK. Depending on what OS the Raspberry Pi is running, it may include support for SAS tokens.

Did you have a look at the Azure IoT Hub library and its associated Azure IoT Hub sample? The Azure IoT Hub library provides an API to connect to an Azure IoT Hub instance and interact with it. It connects to Azure IoT Hub using MQTT over TLS.

<wrn> modem_key_mgmt: Failed to retrieve CMEE status, err -1

<err> Lesson4_Exercise2: Failed to provision CA certificate: -1

The output tells us that you have not provisioned the certificates, see Prerequisites for connecting to Azure IoT Hub. 

There is a MQTT Azure sample available in the Zephyr repository, but this is not tested with the nRF9160. It might be beneficial to look at how this sample, however, it does seem to be intended for ethernet connection.

Kind regards,
Øyvind