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Create and Configure OPC Toolbox Objects

This example shows you how to create and configure OPC Toolbox™ objects.

PREREQUISITES:

Create Client Objects

Create a client using the opcda function. You need the host name and the server ID for the OPC Server associated with this client.

da = opcda('localhost','Matrikon.OPC.Simulation.1');
connect(da);

Add Groups to the Client

Use the addgroup function to add groups to the client object. The OPC Toolbox automatically assigns a name to the group, if you do not specify one.

grp1 = addgroup(da);

Group objects are used to manage collections of daitem objects.

To assign your own name to a group, the name must be unique for all the groups in a client. Pass the name as an additional argument to addgroup.

grp2 = addgroup(da,'MyGroup');

Type the object name to view a summary of the group object.

grp1
grp1 =

Summary of OPC Data Access Group Object: Group0

   Object Parameters
      Group Type   : private
      Item         : 0-by-1 daitem object
      Parent       : localhost/Matrikon.OPC.Simulation.1
      Update Rate  : 0.5
      Deadband     : 0%

   Object Status
      Active       : on
      Subscription : on
      Logging      : off

   Logging Parameters
      Records      : 120
      Duration     : at least 60 seconds
      Logging to   : memory
      Status       : Waiting for START.
                     0 records available for GETDATA/PEEKDATA

Add Item Objects to the Group

Add the item named Random.Real8 to the group.

itm1 = additem(grp1,'Random.Real8');

If you want the value stored in MATLAB® to have a specific data type, specify it as the third argument.

itm2 = additem(grp1,'Random.UInt2','double');

To view a summary of the object, type the name of the object.

itm1
itm1 =

Summary of OPC Data Access Item Object: Random.Real8

   Object Parameters
      Parent        : Group0
      Access Rights : read

   Object Status
      Active        : on

   Data Parameters
      Data Type     : double
      Value         : 0
      Quality       : Bad: Out of Service
      Timestamp     : 12-Apr-2016 16:19:50

Create Object Vectors

References to multiple OPC Toolbox objects can be stored in object vectors.

itmVec = [itm1,itm2]
itmVec =

   OPC Item Object Array:

   Index:  Active:  ItemID:             Value:                Quality:    TimeStamp:
   1       on       Random.Real8        0                     Bad: Ou...  16:19:50
   2       on       Random.UInt2                              Bad: Ou...   

Displaying the object vector shows information about each object in the vector.

View and Change Object Properties

View a list of all properties supported by the object.

get(da)
  General Settings:
    EventLog = []
    EventLogMax = 1000
    Group = [1×2 dagroup]
    Host = localhost
    Name = localhost/Matrikon.OPC.Simulation.1
    ServerID = Matrikon.OPC.Simulation.1
    Status = connected
    Tag = 
    Timeout = 10
    Type = opcda
    UserData = []

  Callback Function Settings:
    ErrorFcn = @opccallback
    ShutdownFcn = @opccallback
    TimerFcn = []
    TimerPeriod = 10

Obtain information about a specific property.

clientName = da.Name
clientName =

localhost/Matrikon.OPC.Simulation.1

Get information about a property using the propinfo function.

statusInfo = propinfo(da,'Status')
statusInfo = 

               Type: 'string'
         Constraint: 'enum'
    ConstraintValue: {'disconnected'  'connected'}
       DefaultValue: 'disconnected'
           ReadOnly: 'always'

The information includes whether the property is read-only, and lists the valid values for properties that have a predefined set of values.

Set the value of the Timeout property to 30 seconds.

da.Timeout = 30
da =

Summary of OPC Data Access Client Object: localhost/Matrikon.OPC.Simulation.1

   Server Parameters
      Host      : localhost
      ServerID  : Matrikon.OPC.Simulation.1
      Status    : connected
      Timeout   : 30 seconds

   Object Parameters
      Group     : 2-by-1 dagroup object
      Event Log : 0 of 1000 events

Clean Up

Delete objects that you are finished using from the OPC Toolbox engine.

disconnect(da)
delete(da)

Deleting the client object also deletes the group and item objects associated with that client.

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