Echelon LNS - Manual (Page 105)

LNS Programmer's Guide 91
Discovering and Installing Devices
There are several main phases involved in the automatic installation scenario depicted in
Figure 5.5. These phases are listed below:
1. The first step is to discover the devices that have been added to the network. There
are several ways to discover new devices. For more information, see Discovering
When New Devices are Attached to the Network on page 91.
2. Once you have discovered a new device, you need to define and configure the device
in the LNS database, and connect it to other devices on your network. For more
information on these tasks, see Installing Devices on page 93.
3. You will also need to program your application to determine when devices are
removed or replaced on the network, and update the LNS database accordingly. For
more information on this, see Discovering When Devices are Detached or Replaced on
page 96.
Discovering When New Devices are Attached to the Network
The first major step in the automatic installation scenario is for the application to
discover the devices that are attached to the network. There are three ways your LNS
application can do so:
• Allow the LNS Object Server to discover the devices using the
background discovery process. Devices discovered by this process will be
represented as AppDevice objects in the
Discovered.Uninstalled
subsystem. The
Discovered.Uninstalled
subsystem is managed by
LNS. The background discovery interval determines the time it will take
for the LNS Object Server to find a device. The default for this interval is
180 seconds, and you can change this value by writing to the
System
object’s DiscoveryInterval property. If a device is configured, the
background discovery process will ignore it. Therefore, the background
discovery process will not discover configured devices that you move from
one network to another. For this reason, device designers usually provide
a mechanism within an application that will deconfigure a device when it
is moved. For example, if the application detects an asserted service pin
for 10 seconds following a power cycle, it could call the Neuron C
go_unconfigured() function.
When using this approach, you should use the System object’s
BeginChangeEvent() method to subscribe your application to the
OnChangeEvent events. Once you do so, LNS will generate an
OnChangeEvent event each time it discovers a new device or router on
the system. See the LNS Object Server Reference help file for more
information on the OnChangeEvent event.
Note that the OnChangeEvent event reports changes to the LNS network
database. Thus, by the time the OnChangeEvent reports the detection of
a new physical device, the AppDevice object associated with that device
exists in the network database and is ready for use by your application.
Subscribing to the related OnAttachment event provides similar
information, but relates to network operations. Thus, an AppDevice
object associated with a physical device may not have been added to the