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Transmit Operations
Each Xbee unit comes flashed with a factory default address that cannot be modified. Using this, Xbee modules can choose to either Unicast a packet to a specific module based on its source address, or Broadcast to all nodes. To do this, in every TX packet, you can define a Destination address to send the packets to. If this address is equal to 0xFFFF (with everything else 0), the packet will be broadcasted. Otherwise it will be unicasted to that node.
There is an acknowledgement (ACK) between two nodes during a Unicast. There is none for broadcasting. Hence, Unicast is the preferred method of transferring data between nodes.
The modules are also configured to use the Point to Point/Multipoint delivery method. Xbee's also support the Repeater/Directed Broadcast and Digimesh methods, which are ways of leveraging multiple nodes to act as repeaters to increase range. Because we only fly with 2 nodes, one on the ground and one on the plane, this functionality is not used.
Configuring the Modules with XCTU
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After downloading the software, the module you're configuring needs to be plugged in to an Xbee mini-USB adapter. You cannot cannot use the Xbee breakout used for the Picpilot to configure the modules from your PC, unless you configure remote AT commands, which it too complicated to describe.
Connection Settings
All of the modules should be configured to connect via UART at 115200 baud/s, 8N1 (1 stop bit, no parity). If this doesn't work initially, try re-plugging in the usb adapter from your PC. Note that by default the modules come pre-configured to connect at 9600baud/s, so if the Xbee was just bought, use that.
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