Rapidly Integrating ZigBee Smart Energy

By MMB Research

Contributed By Digi-Key Corporation


For the past 10 years or more, electrical utilities have pushed to upgrade to a Smart Grid, which provides consumers with greater access to information, and utilities with opportunities for managing electrical demand. This push led to the development of the ZigBee Smart Energy open standard and adoption of ZigBee wireless communication in the majority of Smart Meters in North America. The Smart Energy standard has rapidly evolved to allow secure, robust, and reliable communication between a Smart Meter or gateway and devices within a home. However, the onus has been placed on device and appliance manufacturers to adapt their products to the standard and ensure that they can effectively interoperate with other devices on a ZigBee network.

Though critical to their product's functionality, integrating a common, open standard is arguably the least value-adding component of a device or appliance manufacturer's development efforts, and yet it consumes a disproportionate amount of resources and time. Unfortunately, those who may excel at creating appliances and devices often lack similar expertise in wireless and embedded technologies; specifically, the Smart Energy standards that they will need to be intimately familiar with in order to build and support a robust and interoperable solution. Furthermore, as Smart Energy evolves, vendors will have to recommit these resources to comply with new iterations of the standard.

MMB Research has allowed these companies to leapfrog this difficult stage, and bring their products to the Smart Energy market in a cost-effective, timely, reliable, and well-supported manner with a family of Smart Energy products and services built upon the RapidSE platform.

RapidSE embedded software

The RapidSE embedded software platform is at the core of all of MMB’s products and services. It takes the form of a firmware package that is installed on a ZigBee radio chip; in its current and most common incarnation, an Ember EM357 chip.

RapidSE is a fully implemented ZigBee Smart Energy application that supports all of the functionally as set forth in the Smart Energy 1.1 specification. RapidSE fully automates all of the complex functions and logic prescribed by the Smart Energy specification, abstracting those functions out to a simple set of commands comprising the RapidSE Serial Protocol, through which the processor in an OEM customer’s device can interface.

Automating and abstracting the application layer is a novel approach amongst Smart Energy implementations, but the uniqueness of RapidSE goes beyond simply relocating the Smart Energy intelligence. Building a Smart Energy application that can perform reliably in the real world is not just a matter of implementing the specifications. The specification only defines the information model — not the best (or any) methods for actually implementing an application to manage that information. In RapidSE, we have implemented Smart Energy in a highly efficient, robust, and fault-tolerant fashion — an achievement based on our extensive expertise and experience.

Where RapidSE fits

The diagram below illustrates where RapidSE fits in and interacts amongst all the ZigBee hardware and software layers.

Where RapidSE Fits

Application layer | RapidSE

The application layer sits above the network stack, and provides an interface between the stack and the device’s logic. The location of this layer depends on the technology platform used and the approach of the developer implementing it; the application layer can exist on the host device’s processor, interacting with a simpler ZigBee radio chip, or it can exist on a more advanced radio chip such as the Ember EM357 used in our RapidSE ZigBee Module.

It is within this application layer that all of the logic and functionality required by the Smart Energy profile is implemented. This layer is unique to MMB Research and greatly simplifies the OEM’s ZigBee integration efforts.

The RapidSE serial protocol

The RapidSE Serial Protocol, proprietary to MMB products, is the means through which the OEM device’s processor (or in some cases, the Virtual Host software module) interfaces with the RapidSE software. It is similar to an API.

An example can help illustrate this simplification. Consider a Smart Energy-enabled device using RapidSE, such as a thermostat, which wants to join a user’s Smart Energy network. The user has initiated the joining procedure by pressing a button on the device.

The OEM device:
  • Issues the “Join Network” RapidSE command, with a few parameters, to the embedded RapidSE module.
The RapidSE application:
  • Scans all channels for networks (unless a particular one is specified).
  • Screens each returned beacon to validate that it is a compliant network with a valid stack profile.
  • Attempts joining the found network.
  • If the network rejects it, continues to attempt joining any other valid network found during the initial search.
  • Once joined, discovers all of the endpoints and clusters (services) on the joined device (usually the network coordinator).
  • Validates that said device supports at least the mandatory minimum set of clusters.
  • Initiates CBKE (Certificate Based Key Establishment, applying ECC).
  • Searches out other server clusters on the network (in the case of Multi-ESI networks).
  • Registers, with any server clusters found and the services that the host specifies it wants to support.
  • Calls the various ”get” query commands (i.e. Get Scheduled Prices, Get Last Message, etc.) to ensure the device has the most up to date Smart Energy information from all the various sources on the network.
  • Processes any responses to those commands, validating them for business logic and security before relaying them to the host.
  • Reports the successful join to the host.
The OEM device is now joined.

It is clear from this example that the RapidSE application removes a significant portion of the development burden by automating the series of events that must happen according to the ZigBee Smart Energy profile, drastically reducing the amount of input required from the host. In addition to the extensive simplification that comes with using the RapidSE serial protocol, the RapidSE application also grants confidence that the solution will be able to interoperate with Smart Energy devices from a plethora of vendors. Within many of the steps described above, there are varying interpretations of the ZigBee standard that can present interoperability challenges. At MMB, we have already learned those lessons in testing labs, utility pilots, and in the field, and have folded constant improvements into our RapidSE application to ensure that our customers will be able to interoperate with the devices of their choosing.

RapidSE consulting services

The Virtual Host is an optional layer unique to RapidSE, and a key advantage of our platform. Typically, developers would program their devices to interact with our software via our RapidSE Serial Protocol. This is often the case for customers developing new products or adding connectivity to products that have never had communications or control capabilities.

RapidSE Consulting Services

In our Virtual Host layer, we have created the ability to adapt RapidSE to pre-existing serial protocols used by customers bound to legacy systems. Provided that a customer’s protocol has reasonably analogous functions or commands to those present in Smart Energy, we can create a logical mapping to that existing functionality. This allows developers to integrate RapidSE — and ZigBee Smart Energy — without any modifications to their hardware/software, avoiding the accompanying political or bureaucratic barriers.

To take advantage of this benefit, customers engage us in a Non-Recurring Engineering (NRE) contract to write a Virtual Host layer compatible with their protocol.

Adapting to device logic


Device Logic refers to the intelligence and logic of the OEM device itself. This is the only part that remains the responsibility of the OEM; and rightly so, as it is the only part that defines their specific device’s unique behavior. For instance, RapidSE may report a call for shedding its load by 25 percent, but only the OEM can decide what that means for their device. Some examples of different device logic include:
  • Pool Pump - Reduce water flow
  • Air Conditioner - Adjust temperature set point
  • Energy Display - Indicate an event has been received
  • Integrated Energy Management System - Coordinate a variety of devices to achieve a load reduction.
Each vendor must decide how their device interacts with Smart Energy information. In fact, that is where a vendor’s competitive advantage may lie. Typically, this logic resides on the device’s processor itself.

Is customization always required?


We have discussed Virtual Hosts, contract engineering for value-added functionality, and other customizations. Yet we also tend to refer to RapidSE with terms like turnkey and off-the-shelf, and this may create some confusion or lead one to believe that RapidSE must be tailored to individual OEM’s, products, or applications.

To clarify, RapidSE works as described out of the box, a fully automated Smart Energy solution with no customization necessary. Yet it is also a flexible platform that can adapt to customer needs. The number of unique applications in the market today necessitates flexibility. With RapidSE, value-added functionality can be built on top of the immense amount of work already performed by our platform. Furthermore, we have accommodated this flexibility in a number of ways. Virtual Hosts allow us to adapt to customers’ existing products; custom clusters allow us to develop custom value-added functionality on behalf of our customers for a tailored build of our software; and custom messaging features built into RapidSE allow customers to pass their own payloads through RapidSE, should they wish to add that functionality to the their device.

Customization examples

For example, a manufacturer of automated window covering controls has contracted us to develop an entirely custom assembly (containing our module) that will communicate using their pre-existing proprietary protocols. In addition to time savings, our knowledge of ZigBee networks and HAN devices allows us to develop practical and robust testing and qualification standards for these projects (and their products). However, our services are not limited to resource reallocation and testing.

RapidSE has enabled our customers to leapfrog the broad range of activities required to achieve baseline ZigBee connectivity, and more immediately pursue advanced value-added development utilizing our expertise. We have developed and integrated a wide array of manufacturer-specific, value-added functions into their RapidSE-based applications.

Our contract services allow us to engage with customers that otherwise would face technical or political hurdles in integrating our platform. Sometimes customers already have proprietary or legacy hardware configurations for communications modules that we can work to adapt. For instance, a load controller vendor had already designed their product to accommodate a competitive hardware module. We were able to quickly build “daughter boards” that adapted our module to their sockets — a task we have engaged in numerous times for a variety of vendors.

Conclusions

The Smart Energy market is evolving quickly. Utilities and appliance vendors are finding themselves developing products in areas that lie outside of their core expertise, all in the name of empowering consumers with the access to information and degree of control that they demand. Given the importance of rapidly going to market with a robust and reliable solution, MMB’s RapidSE product family is indispensable. RapidSE significantly reduces the development burden by abstracting the complex functions and logic of ZigBee Smart Energy into the easily mastered RapidSE Serial Protocol, while maximizing flexibility and interoperability with an ever-evolving solution behind the scenes.
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