The much anticipated Zigbee Smart Energy Profile 2.0 was recently released. Representing an effort spanning more than three years, this milestone includes contributions from NIST, IETF and the Zigbee Alliance. Various companies also participated in the initiative, including utility, meter, silicon and software stack vendors.
Smart Energy – the application profile that drove the Zigbee Alliance development of the Zigbee IP (ZIP) – is the first public profile requiring ZIP instead of the current Zigbee and Zigbee PRO underlying stacks. Zigbee IP (ZIP) and SEP 2.0 offer TCP/IP based interoperability for smart energy networks, thereby facilitating participation in the Internet of Things (IoT) without the need for special gateways. In fact, ZIP is designed to be physical layer (phy) agnostic and is capable of running across various platforms including 802.15.4 Wireless, WiFi, Power Line Carrier Ethernet and more.
SEP 2.0 is built using numerous mainstream protocols such as TLS/HTTPS, XML, EXI, mDNX and REST. Each SEP 2.0 device boasts an optimized HTTP server serving up and responding to data objects defined by an XML schema. Security is ensured by familiar HTTPS with strong authentication, while an RFC compliant IPv6 stack provides the network with specific routing and translation layers for the wireless PHY. The SEP 2.0 presentation from the Zigbee Alliance is available here [PDF].
Two recommended implementation strategies for SEP 2.0 in devices are Single Chip and Multi-Phy. Single Chip implementations use a dedicated microcontroller and RF transceiver (or a combined SoC) running a dedicated stack. This strategy works particularly well when adding Zigbee SEP 2.0 support where there is no other network or TCP/IP stack in low to mid range devices. A good example might be a thermostat or load control device, both of which require communications with other smart energy devices – even if they are equipped with a small processor dedicated to the control and UI functions of the device.
The Multi-Phy implementation – a new way of looking at Zigbee – offers advantages in devices equipped with multiple network interfaces and/or a capable processor such as an Atmel SAM4, SAM9, or SAMA5 MPU or MCU. In such cases, the 802.15.4 transceiver (like the AT86RF233) becomes the network interface PHY layer underneath the IPv6 stack and SEP 2.0 layers running on the processor. Since the IPv6 stack is a compliant implementation, other network PHYs are also supported by the stack. Running two or more physical interfaces with a single processor is certainly not an issue, as devices that communicate via Zigbee, WiFi, PLC, and Ethernet can be designed. Because a single processor and IPv6 stack are used, the cost will ultimately be lower than duplicating these functions in a separate chip dedicated to Zigbee SEP 2.0.
Single Chip and Multi-Phy implementation
The multi-phy implementation is also ideal for gateway devices bridging different physical layers. And since SEP 2.0 is built using standard web protocols, once you bridge the smart energy network to the Internet, managing your home energy devices from a tablet or smartphone is no stretch at all and brings us closer to the reality of the Internet of Things (IoT).
Atmel, along with software stack partner Exegin Technologies, offers robust and compliant solutions for Zigbee IP and SEP 2.0. There is already interest from leading networking and utility companies, with deployment of certified devices expected before the end of 2013. The critical design decision most of us have to consider? Whether to dedicate the cost and complexity of a single chip Zigbee solution – or optimize it and lower cost with a software stack and radio transceiver solution that offers shared resources and the possibility of multiple networks.
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