Joining ZigBee networks

ZigBee networks are called Personal Area Networks or PANs. In the ZigBee protocol, the only node that can start a new network is the coordinator. For that reason, each ZigBee network must have one coordinator.

XBee Gateway includes a built-in XBee ZigBee node already configured as coordinator. Therefore, as soon as you power on the XBee Gateway device, your ZigBee network is initialized.

To start a network, the coordinator must automatically choose a PAN identifier (PAN ID) and the operating channel for that network. Once those parameters are established and the network is initialized, the coordinator and routers can allow other devices (other routers or end devices) to join the network and route data.

Each network is defined with a unique PAN identifier (PAN ID). This identifier is common among all devices of the same network. That is, devices on the same ZigBee network must share the same PAN ID in order to communicate with each other. When you power on a coordinator, it automatically establishes the PAN ID or uses a pre-configured one when it creates the new network.

• If the PAN ID of the coordinator is 0, it performs a PAN scan to identify nearby ZigBee networks and uses a random unused PAN ID to start the new network. By default, an XBee Gateway coordinator is configured to generate a random PAN ID.
• If the PAN ID for a router or end device is 0, it performs a PAN scan and tries to join any available ZigBee network it finds.

You can connect to an XBee ZigBee module that is configured as a router node to the network initialized by XBee Gateway. By default, the PAN ID of this ZigBee module is configured to 0. Therefore, if you power on the XBee ZigBee module and there is no other ZigBee network around, the module joins the ZigBee network initialized by XBee Gateway automatically. The joining operation occurs when the Association LED of the board on which the XBee ZigBee module is mounted starts blinking.

The 802.15.4 PHY (physical layer) protocol description defines 16 operating channels in the 2.4 GHz frequency band. Before starting the network, the coordinator automatically performs a channel scan to select a good channel to use for the network.

You can configure all the ZigBee nodes in a network with the channel or channels on which they operate.