Digi XBee-PRO XSC - Page 45

XBee‐PRO®900HP/XBee‐PRO®XSCRFModules
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1. If a preferred sleep coordinator is going to be used in the network, deploy it first. If there will be no
preferred sleep coordinator, select a node for deployment, power it on and press the commissioning button
twice. This will cause the node to begin emitting sync messages.
Verify that the first node is emitting sync messages by watching its associate LED. A slow blink indicates that
the node is acting as a sleep coordinator.
2. Next, power on nodes in range of the sleep coordinator or other nodes which have synchronized with the
network. If the synchronized node is asleep, it can be woken by pressing the commissioning button once.
3. Wait a cycle for the new node to sync itself.
4. Verify that the node syncs with the network. The associate LED will blink when the module is awake and
synchronized.
5. Continue this process until all nodes have been deployed.
Adding a New Node to an Existing Network
To add a new node to the network, the node must receive a sync message from a node already in the network.
On power-up, an unsynchronized sleep compatible node will periodically send a broadcast requesting a sync
message and then sleep for its SP period. Any node in the network that receives this message will respond
with a sync. Because the network can be asleep for extended periods of time, and as such cannot respond to
requests for sync messages, there are methods that can be used to sync a new node while the network is
asleep.
1. Power the new node on within range of a sleep support node. Sleep support nodes are always awake and
will be able to respond to sync requests promptly.
2. A sleeping cyclic sleep node in the network can be woken by the commissioning button. Place the new node
in range of the existing cyclic sleep node and wake the existing node by holding down the commissioning
button for 2 seconds, or until the node wakes. The existing node stays awake for 30 seconds and will respond
to sync requests while it is awake.
If you do not use one of these two methods, you must wait for the network to wake up before adding the new
node. The new node should be placed in range of the network with a sleep/wake cycle that is shorter than the
wake period of the network. The new node will periodically send sync requests until the network wakes up and
it receives a sync message.
Changing Sleep Parameters
Changes to the sleep and wake cycle of the network can be made by selecting any node in the network and
changing the SP and/or ST of the node to values different than those the network is currently using. If using a
preferred sleep coordinator or if it is known which node is acting as the sleep coordinator, it is suggested that
this node be used to make changes to network settings. If the network sleep coordinator is not known, any
node that does not have the non-sleep coordinator sleep option bit set (see the SO command) can be used.
When changes are made to a node’s sleep parameters, that node will become the network’s sleep coordinator
(unless it has the non-sleep coordinator option selected) and will send a sync message with the new sleep
settings to the entire network at the beginning of the next wake cycle. The network will immediately begin
using the new sleep parameters after this sync is sent.
Changing sleep parameters increases the chances that nodes will lose sync. If a node does not receive the
sync message with the new sleep settings, it will continue to operate on its old settings. To minimize the risk
of a node losing sync and to facilitate the re-syncing of a node that does lose sync, the following precautions
can be taken:
1. Whenever possible, avoid changing sleep parameters.
2. Enable the missed sync early wake up sleep option (SO). This command is used to tell a node to wake up
progressively earlier based on the number of cycles it has gone without receiving a sync. This will increase the
probability that the un-synced node will be awake when the network wakes up and sends the sync message.
Note: using this sleep option increases reliability but may decrease battery life. Nodes using this sleep option
which miss sync messages will have an increased wake time and decreased sleep time during cycles in which
the sync message is missed. This will reduce battery conservation.
3. When changing between two sets of sleep settings, choose settings so that the wake periods of the two
sleep settings will happen at the same time. In other words, try to satisfy the following equation: (SP1 + ST1)
= N * (SP2 + ST2), where SP1/ST1 and SP2/ST2 are the desired sleep settings and N is an integer.