© 2014 Digi International Inc. 54
XBee/XBee-PRO
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DigiMesh 2.4 User Manual
5 Verify that the node syncs with the network. The associate LED will blink when the module is
awake and synchronized.
6 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.
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