XBee®/XBee‐PRO® ZB SMT RF Modules
A router has the following characteristics: It ...
•Must join a ZigBee PAN before it can transmit, receive, or route data
•After joining, can allow routers and end devices to join the network
•After joining, can assist in routing data
•Cannot sleep--should be mains powered.
•Can buffer RF data packets for sleeping end device children.
An end device has the following characteristics: It ...
•Must join a ZigBee PAN before it can transmit or receive data
•Cannot allow devices to join the network
•Must always transmit and receive RF data through its parent, and cannot route data.
•Can enter low power modes to conserve power and can be battery-powered.
An example of such a network is shown below:
In ZigBee networks, the coordinator must select a PAN ID (64-bit and 16-bit) and channel to start a network.
After that, it behaves essentially like a router. The coordinator and routers can allow other devices to join the
network and can route data.
After an end device joins a router or coordinator, it must be able to transmit or receive RF data through that
router or coordinator. The router or coordinator that allowed an end device to join becomes the "parent" of the
end device. Since the end device can sleep, the parent must be able to buffer or retain incoming data packets
destined for the end device until the end device is able to wake and receive the data.
A module can only operate as one of the three device types. The device type is selected by configuration rather
than by firmware image as was the case on earlier hardware platforms.
By default, the module operates as a router in transparent mode. To select coordinator operation, set CE to 1.
To select end device operation, set SM to a non-zero value. To select router operation, both CE and SM must be
0.
One complication is that if a device is a coordinator and it needs to be changed into an end device, CE must be
set back to 0 first. If not, the SM configuration will conflict with the CE configuration. Likewise, to change an
end device into a coordinator, it must be changed into a router first.
Another complication is that default parameters for a router build don't always work very well for a coordinator
build. For example:
DH/DL is 0 by default, which allows routers and end devices to send data to the coordinator when they first
come up. If DH/DL is not changed from the default value when the device is changed to a coordinator, then the
device will send data to itself, causing characters to be echoed back to the screen as they are typed. Since this
is probably not the desired operation, DH/DL should be set to the broadcast address or some specific unicast
address when the device is changed to a coordinator.
Another example is EO for smart energy builds. This value should be 08 for routers and end devices and it
should be 02 for the coordinator to designate it as the trust center. Therefore, if using authentication, which is
the normal case for Smart Energy builds, EO should be changed from 02 to 08 when CE is set to 1.
In general, when changing device types, it is the user's responsibility to ensure that parameters are set to be
compatible with the new device type.
© 2010 Digi International, Inc.
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DCD [ DIGITAL CORE DESIGN ]
