Echelon LonBridg Server - Manual (Page 52)

46 LonBridge Device Class File
network output polled SNVT_power nvoPower
nv_properties {
cpPwrSendOnDelta
};
The first network variable, nviValue, defines the input state for the simplified
Lamp Module, which the LonBridge application uses to set the lamp’s state. The
second network variable, nvoValueFb, defines the output state for the simplified
Lamp Module, which the lamp uses to report its current state to the LonBridge
application and to the network. And the third network variable, nvoPower,
defines the output power usage for the device, which the lamp uses to report its
power usage to the LonBridge application and to the network.
The next step is to define the network variables within the device class file, that
is, to translate the Neuron C declarations for the network variables into the XML
elements required by the device class file.
Define <nv> Elements
There are two sections within the device class file that define the network
variables (within <nvs> elements). The first section appears within the
<attributes> element:
<attributes>
<attribute name="state">
<nvs>
<nv index="?" direction="input" />
<nv index="?" direction="output" />
</nvs>
</attribute>
<attribute name="power">
<nvs>
<nv index="?" direction="output" />
</nvs>
</attribute>
</attributes>
The state attribute matches two network variables, an input network variable
and an output network variable. Thus, the <nvs> element contains two <nv>
elements, one with direction=”input” and the other with direction=”output”. At
this point, however, the network variable indices are unknown, so they are
marked with a question mark (?).
The
power attribute matches one network variable. Thus, the <nvs> element
contains one <nv> element, with direction=”output”. The network variable index
is unknown, so it is marked with a question mark (?).
See Browse the XIF File to Determine Indices on page 56 to determine the
network variable indices.
The other section that defines network variables within the device class file is the
<nvs> element that is not within the <attributes> element. This section defines
the specific attributes of each network variable:
<nvs>
<nv index="?" direction="input" size="?">
<byte index="?" length="?">
<attribute name="state" enum="true">