Network configurations Basic communications
XBee®-PRO 900HP/XSC RF Modules
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Constraints
n Requires that each device have a unique MY (Source Address) parameter.
n System must introduce just one packet at a time to the network for transmission (256 bytes
max).
n Each hop (H) decreases the network throughput by a factor of 1/(H+1). Additional repeaters
add network redundancy without decreasing throughput.
Required parameter values (TX module): MD = 3 or 4, MY = unique value. Send the AM (Auto-set MY)
and WR (Write) commands to all devices in the network).
Related commands: Networking (MD, DT, MY, AM), Serial Interfacing (RN, PK, RO, RB).
Recommended use: Use in networks where intermediary nodes required to relay data to devices that
are beyond the transmission range of the base device.
Theory of operation
Integrators can extend the effective range and reliability of a data radio system by forwarding traffic
through one or more repeaters.
Instead of using routing tables and path discovery to establish dynamic paths through a network, the
repeater system uses a sophisticated algorithm to propagate each RF packet through the entire
network.
The network supports RF packets of up to 256 bytes. The repeater network can operate using
broadcast or addressed communications for multi-drop networks and works well in many systems
with no special configuration.
When in Repeater Mode, the network repeats each message among all available nodes exactly one
time. This mechanism eliminates the need for configuring specific routes. The network is self-
organizing and self-healing so that the system is able to receive transmissions in the event of a device
going down.
Sample Repeater network topology:
To summarize, the system sends and receives 64 bytes 5 times per second for a throughput of 320
bytes per second with no repeaters and 128 bytes per second with 2 repeaters. Generally, the
network throughput decreases by a factor of 1/(R+1), with R representing the number of repeaters
between the source and destination.
Configuration instruction (Basic Broadcast communications)
Assign each device a unique MY (source) address. The AM (Auto-set MY) command configures a unique
source address based on device serial number.
Enable Basic Broadcast Communications (DT = 0xFFFF) or Addressed Broadcast Communications (DT
specifies a destination).
Configure PK, RO and RB to ensure that RF packet aligns with protocol packet. (for example,
PK=0x100, RB=0x100, RO depends on baud rate).
Configure one or more repeaters in the system (MD = 3).
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