Echelon LNS - Manual (Page 246)

LNS Programmer's Guide 232
Set MyInterface = MyAppDevice.Interface
Set MyVariables = MyInterface.NetworkVariables
Set MyNV = MyVariables.Item(“Input One”)
3. Use the
GetDataPoint()
method to create a
DataPoint
object for the
network variable. The
GetDataPoint()
method takes a single input
parameter that must be set to 0.
Set MyDataPoint = MyNV.GetDataPoint(0)
4. To set the value of the network variable through the
DataPoint
object,
set the
Value, RawValue,
or
FormattedValue
properties, and then
call the
Write()
method. You do not need to call
Write()
if the
DataPoint object’s AutoWrite
property is set to
True
.
MyDataPoint.Value = 1000
MyDataPoint.Write()
5. To read the value of the network variable through the
DataPoint
object,
call the
Read()
method and then read the value via the
Value,
RawValue
or
FormattedValue
properties. You do not need to call
Read()
if the AutoRead property is set to
True
.
MyDataPoint.Read()
Dim Value as String
Value = MyDataPoint.FormattedValue
When reading the value of a
DataPoint
object, there are many ways for
an application to determine how the data will be displayed. For more
information on this, see Data Formatting on page 241. Consult the LNS
Object Server Reference help file for a complete list of the properties and
methods of the
DataPoint
object.
The type of data that is stored in a network variable is determined by its base type. As of
LNS Turbo Edition, you can modify a network variable’s type by writing to its TypeSpec
property, as long as the network variable is on a device that supports changeable types.
For more information on this, see Changeable Network Variable Types on page 185.
Data Points and Enumerated Types
When reading or writing network variables and configuration properties with
DataPoint objects, you should note that some standard and user-defined types are
defined as enumerated data types in the resource files. A network variable or
configuration property that uses an enumerated type will only accept values that belong
to the enumeration referenced by the type it is using.
For example, the SNVT_defr_term type is based on the "defrost_term_t" enumeration
type. As defined in the standard LonMark resource files, the defrost_term_t enumeration
type contains values between -1 and 100. However, not all the values in this range are
associated with the type’s enumeration members. Values from 9 to 99 are illegal, since
there are no enumeration members associated with them. Each legal value is assigned an
enumeration name. If you have a network variable or configuration property that is
using an enumeration data type, you can only write the enumeration names defined for
that type to the object’s value.
Consider a case where you have acquired a data point for a network variable using the
SNVT_defr_term type. In this situation, you will only be able to write enumeration