Echelon LNS - Manual (Page 132)

LNS Programmer's Guide 118
2. Get the AppDevices collection from this subsystem and iterate through
the devices by index, using the Item property. To find the target,
examine the properties of each AppDevice in the collection. For example,
the program ID, channel ID, and location can be used to find the
appropriate devices.
The location field is a 6-byte field in the Neuron Chip used for storing
installation-related information. This property is intended for use in
situations where the device’s physical location may be read from its I/O
pins or programmed into the device prior to installation. For example, if a
device is installed in a slot in a card cage, it can read the slot number
from the edge connector.
Set MyAppDevices = MySubsystem.AppDevices
Counter = 1
MySystem.BeginTransaction()
MaxDevices = MyAppDevices.Count
While not DeviceFound and Counter <= MaxDevices
Set MyAppDevice = MyAppDevices.Item(Counter)
DeviceFound = AppDevice.Location = DesiredLocation
Counter = Counter + 1
End While
MySystem.CommitTransaction()
3. To confirm that you have found the correct device, wink the device by
invoking the Wink() method. The device should be programmed to
respond in a way that can be easily detected by the person installing the
device. For example, lights can blink, alarms can ring, and displays can
flash. The person performing the installation can then identify the
physical application device responding to a particular wink message as
the one currently being installed.
MyAppDevice.Wink()
4. Continue performing steps 2 and 3 until the correct device has been
found. Then, commission the device, and add it to connections as your
network design requires.
5. Note that in a fashion similar to the confirmed service pin protocol
described earlier, a local technician could confirm the correct device
performed the wink action by activating the device’s service pin. Your
application could obtain that service pin message via the
OnServicePinEvent event, and then compare the originator device’s
Neuron ID with the value stored in the NeuronId property of the
CurrentDevice returned by the event. If both match, your application
could assume that the detected device is the desired one.
In a fully automated approach, your application could use other methods
to confirm the device’s identity. For example, the application could
compare the device’s program ID with the expected value, it could query
the device’s Location property, or inspect the channel it is attached to
by reading the AppDevice object’s Channel property.
The LNS Object Server can also find configured devices. An LNS application may invoke
DiscoverDevices() method on a system to discover configured devices that have not
been added to the LNS database. When you call DiscoverDevices(), you must specify
the DomainId and backgroundReg parameters. These specify the domain on which
devices will be discovered, and whether registration will take place as a background or