Connect Modes of Operation#
Connect supports three distinct modes of operation. Only one mode is allowed in any single network and there is no simple way to upgrade from one mode to the other. As a result, you should select the mode carefully early in the design process.
Extended Star Mode#
In this mode, Connect supports star and extended star topology networks per the following figure.
Extended Start Mode supports the following device types.
Device | Indicator | Description |
|---|---|---|
Star coordinator | Blue circle | The star coordinator forms and manages the star or extended star network. The star coordinator also communicates with other range extenders and end nodes. Each Connect star network has a single coordinator. |
Star range extender | Red circle | A device between the star coordinator and one or more star end nodes that can be used to extend the range of the star end nodes. |
Star node | White circle | Joins to a star coordinator or a star range extender. |
Data message routing between any two devices is supported by the network layer in this mode. Extended star topology is a centralized network. Hence, joining to the network requires acceptance by the Personal Area Network (PAN) coordinator. Short address allocation and assignment can be handled by the PAN coordinator. This mode is not fully IEEE 802.15.4 compliant.
Direct Mode#
In this mode, Connect only provides connections between devices that are in range of each other (see the figure below). This is not a centralized topology.
Direct mode supports the Direct device type, which send (and receive) messages to (and from) other (Direct) devices in range on the same PAN, with no star topology restrictions. Message forwarding can be implemented in an upper layer.
The Connect network layer is still enabled in this mode, but it does not provide routing, only endpoints. Routing protocols can be implemented in the application layer. Any device can join the PAN by setting the right PAN parameters. Short address allocation is not provided by the Connect stack and address duplication must be avoided by the application. This mode is not fully IEEE 802.15.4 compliant.
MAC Mode#
MAC mode supports the MAC device type, which send and receive standard 802.15.4 messages from other 802.15.4 devices in range. Message forwarding can be implemented in an upper layer.
MAC mode is a fully IEEE 802.15.4 compliant setup of the Connect MAC layer; the network layer is not enabled. The API is more complex compared to Direct mode and requires some knowledge of the IEEE 802.15.4 standard. To make it fully IEEE 802.15.4 compliant, make sure to set up an IEEE802.15.4 compliant radio configuration.
Examples of Connect Modes and Network Topologies#
An example of a Connect network is a network of temperature and humidity sensor end nodes installed throughout a home. Each end node periodically takes a reading and transmits that data either directly to a coordinator (sink) or, for those sensors placed farther away from the coordinator, to a range extender. The range extenders take data from the sensors and forward them to the coordinator. The coordinator not only forms and manages the network, but also sends the compiled data to an environmental management system that is part of another network.
Another example is a topology of two minimally-featured nodes that exchange data in both directions. This topology can be used as a generic wire replacement.
A third example is a topology of N direct devices or MAC devices all in range that exchange data between any pair of two nodes in both directions in a single-hop fashion.