Data source options – Echelon LNS User Manual

Page 250

LNS Programmer's Guide

236

ConfigProperty

is not an array, specify 0 as the index parameter.

The second parameter is the options element. This determines how

LNS will apply changes you make to the

DataPoint

object to the LNS

database, and to the physical device on the network. For more

information on this, see the next section, Data Source Options.

Note that you can change both of these options later by modifying the
DataPoint object’s SourceIndex or SourceOptions properties.

3. To set the value of the configuration property through the

DataPoint

object, set the

Value, RawValue

FormattedValue

property, and

then call the

Write()

method. Note that you do not need to call

Write()

if the

AutoWrite

property is set to

True

MyDataPoint.Value = 1000
MyDataPoint.Write()

NOTE: The Value, RawValue and FormattedValue properties of
DataPoint objects acquired through configuration properties that use

enumerated data types have special behavior that you should be aware
of. For more information, see Data Points and Enumerated Types on page

232.

4. To read the value of the configuration property through the

DataPoint

object, call the

Read()

method and then read the value through the

Value

FormattedValue

properties. You do not need to call

Read()

the AutoRead property is set to

True

Dim Value as String
MyDataPoint.Read()
value = MyDataPoint.FormattedValue

When reading a

DataPoint

object’s value, there are many ways for the

application to affect how the data will be displayed. For more information
on this, see Data Formatting on page 241.

NOTE: Data points are very useful when reading and writing formatted data, or when

accessing an entire raw data value as a whole. However, if you want to access arbitrary

bytes of raw data to read or write a range of elements in a configuration property array,
you should not use a data point. Instead, you should use the GetRawValuesEx() and
SetRawValuesEx() methods of the ConfigProperty object. See the LNS Object Server

Reference help file for more information on these methods.

Data Source Options

When you call the

GetDataPoint()

method, you will use the

options

parameter to

specify how LNS will manage differences that may exist between the value of the

ConfigProperty

in the LNS database and the value of the configuration property in the

physical device on the network when you read or write to the

DataPoint

. Table 9.4

describes the values you can apply to the

options

element.

Note that the value you choose as the options parameter is stored in the

DataPoint

object’s

DataSourceOptions

property. If desired, you can change this setting later.