Network configurations
Network identifiers
XBee/XBee-PRO DigiMesh 2.4 RF Module User Guide
54
Network identifiers
You define DigiMesh networks with a unique network identifier. Use the
ID
command to set this
identifier. For devices to communicate, you must configure them with the same network identifier and
the same operating channel. For devices to communicate, the
CH
and
ID
commands must be equal on
all devices in the network.
The
ID
command directs the devices to talk to each other by establishing that they are all part of the
same network. The
ID
parameter allows multiple DigiMesh networks to co-exist on the same physical
channel.
Operating channels
The XBee/XBee-PRO DigiMesh 2.4 operates over the 2.4 GHz band using direct sequence spread
spectrum (DSSS) modulation. DSSS modulation allows the device to operate over a channel or
frequency that you specify.
The 2.4 GHz frequency band defines 16 operating channels. XBee devices support all 16 channels and
XBee-PRO devices support 12 of the 16 channels.
Use the
CH
command to select the operating channel on a device.
CH
tells the device the frequency to
use to communicate.
For devices to communicate, the
CH
and
ID
commands must be equal on all devices in the network.
Note these requirements for communication:
n
A device can only receive data from other devices within the same network (with the same
ID
value) and using the same channel (with the same
CH
value).
n
A device can only transmit data to other devices within the same network (with the same
ID
value) and using the same channel (with the same
CH
value).
Unicast addressing
When devices transmit using DigiMesh unicast, the network uses retries and acknowledgments
(ACKs) for reliable data delivery. In a retry and acknowledgment scheme, for every data packet that a
device sends, the receiving device must send an acknowledgment back to the transmitting device to
let the sender know that the data packet arrived at the receiver. If the transmitting device does not
receive an acknowledgment then it re-sends the packet. It sends the packet a finite number of times
before the system times out.
The
MR
(Mesh Network Retries) parameter determines the number of mesh network retries. The
sender device transmits RF data packets up to
MR
+ 1 times across the network route, and the
receiver transmits ACKs when it receives the packet. If the sender does not receive a network ACK
within the time it takes for a packet to traverse the network twice, the sender retransmits the
packet.
If a device sends a unicast that uses both MAC and NWK retries and acknowledgments:
n
Use MAC retries and acknowledgments for transmissions between adjacent devices in the
route.
n
Use NWK retries and acknowledgments across the entire route.
To send unicast messages while in Transparent operating mode, set the
DH
and
DL
on the
transmitting device to match the corresponding
SH
and
SL
parameter values on the receiving device.
Содержание XBee DigiMesh 2.4
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