Configure a repeater network
9XTend-PKG-R RS-232/485 RF Modem User Guide
78
Repeater network: configure communications
To configure a Repeater network for Basic broadcast communications:
1. Assign each device a unique MY (source) address. Use the AM command to configure a unique source address
based on the device serial number. This is essential because a unique packet ID on each RF packet is based on the
originator’s MY value.
2. Set DT = 0xFFFF to enable Basic Broadcast communications OR Basic Addressed communications (DT specifies a
specific destination).
3. Configure PK, RO and RB to ensure that the RF packet aligns with the protocol packet. For example:
PK=0x100
RB=0x100
RO depends on baud rate
4. Set MD = 5 to configure one or more devices that you do not intend to be repeaters as repeater End Nodes in the
system.
5. Set MD = 6 to configure remote nodes as destinations. This ensures that the remote node waits for the repeater
traffic to subside before it transmits a response.
To configure a Repeater network for Basic addressed communications, use DT to assign unique addresses to each
device in the network.
Repeater network algorithm details
The firmware uses an algorithm to propagate each RF packet through the entire repeater network. Within a repeater
network, the firmware only defines Repeater Nodes and repeater End Nodes. Repeater Nodes forward messages on
to other devices within range; End Nodes do not.
The algorithm maintains a list of messages previously received in a buffer. The firmware discards messages already in
the buffer. This eliminates End Nodes receiving multiple copies of a packet from more than one source, and also
eliminates multiple repeaters within range of each other from continually passing messages in an infinite loop.
Packet ID (PID) is composed of the TX (transmitting) device MY address and the packet sequence number.
The firmware ignores incoming packets with a PID already in the buffer.
Each device maintains a PID buffer 4-deep of previously received packets (managed as FIFO).
The firmware may shift packets out the serial port and/or repeat them depending on the DT parameter in the RF
packet. The following table shows the basis for these decisions.
Repeat delay based on RSSI
A transmitted packet may be received by more that one repeater at the same time. In order to reduce the probability
that the repeaters will transmit at the same instant, resulting in a collision and possible data loss; the firmware uses
an algorithm that allows a variable back-off prior to a repeater retransmitting the packet. The algorithm allows
devices that receive the packet with a stronger RF signal (RSSI) to have the first opportunity to retransmit the packet.
Address Match
Send out serial port?
Repeat?
Global
Yes
Yes
Local
Yes
No
None
No
Yes