Modbus RTU on Azure IoT Edge

Microsoft is serious about IoT Edge. Azure IoT Edge is now GA for a few months and just last week the version was bumped up to 1.0.1.

The same effort is put into Edge modules. Microsoft provides several modules for different protocols like OPC-UA and Modbus.

In the past I already wrote a couple of times about Modbus TCP in IoT Edge. It’s easy to use and reliable. The Microsoft Modbus module is already available in GA. And I even noticed a reference to “docker pull mcr.microsoft.com/azureiotedge/modbus:1.0”.

If you look deeper into the documentation, you can see that the module supports Modbus RTU too!

It’s always good to learn about other protocols so I arranged some hardware and started a journey.

Let’s see what we need to get started with Modbus RTU.

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Azure IoT Client SDK now supports IoT device modules

Silently, Microsoft introduced modules in IoT Devices.

No, I’m not talking about IoT Edge modules, these are modules for IoT Devices which can connect to the IoT Hub directly.

Before, we used the device client to communicate with clients and the IoTHub. And we used the Device Twin to configure the device with desired properties.

This approach is still valid. But in addition, we can also separate the client logic in multiple modules. And each module can send messages and receive a Module Twin configuration.

Let’s see how this works.

Testing Azure IoTHub Manual failover

The Azure IoTHub is the center of all the IoT efforts of Microsoft. Over the last couple of years (or even months) we see a lot of innovations from that side.

The latest addition is the Manual failover which is now in preview.

This makes it possible to move a complete IoTHub (with eg. all of its devices and routes) to the ‘sister region’. For example, an IoTHub living in West US 2 will move to West Central US. And you can move it back too.

The manual failover is a good starting point for having a more resilient IoTHub. It’s not perfect, there is a chance that unread messages or data is lost. Failover is hard:

But it’s a perfect way to test the ‘automatic’ failover which Microsoft provides when something happens with the region your IoTHub is living in.

I wanted to test this failover. And I wanted to build a client-side solution so I would not lose any messages.

Let’s see how it can be tested.