Taking on Industrial IoT with Real-Time DDS
Source: Bernard Cole

End-to-end latency between publisher and subscriber nodes for various packet sizes over a Gigabit Ethernet connection.

In a move to expand beyond the real-time Data Distribution Services (DDS) middleware it has been providing to military/aerospace and other high-reliability markets, PrismTech has put in place the final building block in its Vortex intelligent data-sharing platform for real-time Internet of Things applications.

That final building block is Vortex Lite, a 400 kilobyte-sized software module that can reside on microcontroller-based systems used in low-latency and resource-constrained Internet of Things (IoT) devices, such as networked sensors, single board computers, embedded gateways and network edge nodes. Vortex Lite is an ultra-light weight implementation of the Object Management Group's (OMG) DDS standard that the company claims delivers deterministic data with an end-to-end latency as low as 30 microseconds over Gigabit Ethernet.

“Over a range of different platforms and operating systems and across a range of packet sizes, we believe that Vortex Lite has the lowest latency of any DDS implementation available on the market,” the company says on its website. This implementation also supports the OMG's Data-Centric Publish-Subscribe (DCPS) minimum profile and the company is already planning for add-ons content-subscription and persistency. And while it is easily portable to a wide range of hardware, board support and open-source operating system platforms, Steve Jennis, SVP Corporate Development, told EE Times that support for pluggable transports is planned for future releases.

While the performance of the Vortex Lite would certainly make it a candidate for many deterministic industrial IoT implementations, that alone would not be enough to set it apart from other offerings, Jennis said. What makes Prism’s implementation unique, he said, is that it is a part of comprehensive intelligent data-sharing platform the company has been developing for the last two years. Vortex Lite has been designed as one of several components that together will allow enterprises to move quickly into the IoT space:

        Vortex Cloud, which extends the capabilities of Vortex Lite with support for data sharing over a Wide Area Network (WAN),
        OpenSplice, a DDS implementation targeted for server-class (desktops, racks etc.) platforms and more specialized real-time embedded environments and operating systems,
        Vortex Café, a "pure" Java DDS implementation specifically optimized for mobile phones and devices, as well as for cloud data sharing,
        Vortex Web, a JavaScript DDS API to use with HTML5/Web-browser apps to send and receive data using the framework’s DDS data backbone,
        Vortex Insight, a set of location independent monitoring and management tools to help configure, tune and test DDS-based IoT systems, and,
        Vortex Gateway, an extensible and configurable protocol gateway framework with support for connectors to over 100 different protocols.

“This last building block is particularly important to enterprises who feel they have missed the IoT boat and are looking for a way to get up to speed quickly,” he said. “To that end, we’ve designed the gateway to be easily integrated with third party legacy applications that may use any number of different communication technologies.”

Where Vortex Lite differs in its “DDS for things” implementation from other publish/subscribe protocols such as AMQP, MQTT, JMS,    REST and CoAP is in its data-centric focus. “Most of these others are message-centric,” said Jennis.    “DDS on the other hand is a data-centric technology. They both can do similar things with respect to providing connectivity in a distributed system, however the way they do it is quite different.”




The 400 kByte Vortex Lite contains all the services needed for an MCU-based IoT end device.

In a message-centric system, the focus is on delivery of the message itself regardless of the data payload it contains, and the infrastructure's role is to ensure that messages get to their intended recipients. “In a data-centric system the focus is on user-defined data,” he said. “The unit of exchange in this type of system is a data value. The data model middleware understands the context of the data and ensures that all interested subscribers have a correct and consistent view of the data.”

This difference is a very important one, Jennis said, especially in many of the IoT applications outside the consumer electronics sector. “Unlike consumer apps, in most industries it is the data and its delivery and context that is paramount, along with when it is delivered and how secure, reliable, and actionable it is.”

The framework also offers another bonus for enterprises looking for a low-risk way to get into the IoT business: real-time DDS was introduced initially in 2003 by the Object Management Group, a consortium that has as its charter the development of enterprise integration standards for a wide range of Web and Internet-based technologies.

The APIs specified by the DDS standard, said Jennis, have been implemented in a range of different programming languages including Ada, C, C++, C#, Java, JavaScript, CoffeeScript, Scala, Lua, and Ruby. “Using standardized APIs also means that DDS applications can be ported easily between different vendor’s implementations,” he said, “especially important for enterprises, which must support diverse software packages, many of which might still find application in this new connected environment.”

The Vortex Lite package also includes an ISO C++ DDS-API for development of code not only for the device, but all of the other elements in the IoT framework it has created. Available with full DDSI rev2.1 interoperability, Vortex Lite can be downloaded for a free 30-day evaluation from PrismTech’s website.

― Bernard Cole, the MCU and PCB Designline editor on EE Times, is an embedded microsystems technology analyst who writes about hardware/software design and use across the range of applications. Contact him at bccole@techrite-associates.com Circle me on Google+.