Echelon LonBridg Server - Manual (Page 53)

LonBridge Server User’s Guide 47
...
</attribute>
</byte>
</nv>
<nv index="?" direction="output">
<byte index="?">
<attribute name="state" enum="true">
...
</attribute>
</byte>
</nv>
<nv index="?" direction="output" size="?">
<byte index="?">
<attribute name="power" length="?" />
</byte>
</nv>
</nvs>
At this point, the <nvs> element is missing important information, such as the
network variable indexes, their lengths, and the byte indexes for fields within the
network variable (if any). However, it does show the three network variables
that the device class file requires for the simplified Lamp Module. In addition,
because the state of the device can be “on” or “off”, the <nv> elements for the
state attribute includes enum=”true” so that we can define an enumeration of the
states.
See
Browse the XIF File to Determine Indices on page 56 to determine the
network variable indexes.
The next step is to determine network variable lengths and byte indexes.
Use the Resource Editor to Determine Attributes
Because the three network variables for the simplified Lamp Module are
standard network variable (SNVT) types, you can use the Echelon NodeBuilder
Resource Editor (or the LONMARK Resource Files Web page, types.lonmark.org )
to determine the attributes of each network variable and network variable field.
You can obtain the most current version of the LonMark Resource Files from
www.lonmark.org/technical_resources/resource_files/ .
For the simplified Lamp Module, the three network variables are declared as:
• SNVT_switch_2 nviValue
• SNVT_switch_2 nvoValueFb
• SNVT_power nvoPower
You can use the Resource Editor to determine the following information about
each of the SNVT types:
• The overall size of the network variable, in bytes
• The byte index value for each field within the network variable
• The length of each field within the network variable, in bytes
• Enumeration values (if any) for network variable fields
• Scaling factors (if any) for network variable fields