Viconics VST5000 (Classic ZigBee) User Guide - Manual (Page 8)

8 VST5000W5000W Wireless Survey Tools User Guide
Orphan Nodes
It is important to understand that if a network is started
up incorrectly it “may” result in orphaned or unassigned
devices / nodes / controllers that will NOT join the ZigBee
network. Let’s first understand how an orphan node is
created. A typical example is when jobs are started on
a technician desk before sending the devices / nodes
/ controllers to the field for installation. Often the
integration technician will begin by powering up the
Jace – coordinator and connect it to the Workbench tool
creating and adding the Wireless Tstat Network driver
layer.
Once the Wireless Tstat Network driver layer is up and
running, the technician will then open and start up the
wireless devices / nodes / controllers one by one and add
them to their Niagara database.
• They will power the first unit, then add it to the
database and finally power it down.
• They will power up the second unit, add it to the
database and then power it down.
• This will be repeated to a maximum of 6 devices.
This will work fine for the first 6 devices only, simply
because the Jace – coordinator can provide a maximum
of 6 assignable addresses. When the technician powers
up the 7th device / node / controller, it will NOT be able
to join the ZigBee network unless one of the previous
device / node / controller is powered back on. Once this
is done, it will be able to assign the next 6 addresses as
usual.
In order to add another 6 devices, one of the previously
added device needs to be left on. If 42 devices are to
be added to the network, 8 of them should ALWAYS be
powered and be within connectivity range of all the
others.
How would orphan nodes appear in the field and how
would you allow them to join the ZigBee network ?
Knowing and understanding
the 6A / 5H rule of ZigBee
ZigBee is a standard which is suitable for wireless sensor
and controller networks. In ZigBee, a device / node
/ controller is said to join a network if it can obtain a
ZigBee network address from a parent device. This
ZigBee address is a value which is NOT initially exposed
or available for the integrator to see.
Devices / nodes / controllers can calculate and assign
addresses for their surrounding devices by a distributed
address assignment scheme. This assignment is flexible,
but it does somewhat restricts the number of attached
devices and the possible depth of the said network for
any given device on the network.
ZigBee supports three kinds of networks type: star, tree,
and mesh networks. The ZigBee coordinator ( In our case,
this is the Jace with the wireless communication card ) is
responsible for initializing, maintaining, and controlling
the network.
• A star network has a coordinator with devices
directly connecting to the coordinator.
• A tree and mesh networks, devices can communicate
with each other in a multi-hop fashion.
The network is formed by one ZigBee coordinator and
multiple ZigBee routers. A device can join a network as
an end device by the associating with the coordinator or
a router.
A ZigBee device / node / controller is said to have
successfully joined a network if it can obtain a ZigBee
network address from the main Jace coordinator or any
other router devices / nodes / controller.
6A stands for 6 addresses maximum
per device / node / controller
Any given device / node / controller including the
Jace –coordinator can ONLY give a maximum 6 ZigBee
addresses out to other devices so they join the active
ZigBee network. This means for any device / node
/ controller to be able to successfully join a ZigBee
network, it needs an address to be assigned by another
device / node / controller which is within connectivity
and that has NOT already assigned its maximum of 6
addresses allowed.
Please note that once a device / node / controller has
been assigned a ZigBee address & has joined the active
ZigBee network, it will save its assigned ZigBee address
to flash memory & re-use it afterwards even after a power
failure or a network re-start. The ONLY time device / node
/ controller would require a NEW ZigBee address is if the
network is re-started with either a new PAN ID or a new
Channel value. This causes the currently assigned & saved
ZigBee address in flash to be erased & will force the /
node / controller to try to re-join a new network.