OPC Toolbox 2.1.4

Creating and Configuring Objects

The OPC Toolbox™ uses three objects arranged in a strict hierarchy. This example shows you how to create and configure these three OPC Toolbox objects, and how to configure OPC Toolbox object properties.

Contents

Step 1: Create Client Objects.

You 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);

Step 2: Add Groups to the Client

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

grp1 = addgroup(da);

To assign your own name (which must be unique for all the groups in a client) you pass the name as an additional argument.

grp2 = addgroup(da, 'MyGroup');

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

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

Step 3: Add Item Objects to the Group

Item objects are added to a group using the additem function. You specify the group object to add the item to, and the Item ID of the server item you want to monitor.

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

To specify a data type for the item (for storage of the value in MATLAB®) you specify the data type as a string.

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         :
      Quality       : Bad: Out of Service
      Timestamp     :

Step 4: Create Object Vectors

You can use object vectors to store references to multiple OPC Toolbox objects. The following example constructs an object vector from the items added to the group. A summary of the object vector shows information about each object in the vector.

itmVec = [itm1, itm2]

itmVec =
   OPC Item Object Array:
   Index:  Active:  ItemID:             Value:                Quality:    Ti
meStamp:
   1       on       Random.Real8                              Bad: Ou...
   2       on       Random.UInt2                              Bad: Ou...

Step 5: Viewing and Changing Object Properties

To view a list of all properties supported by the object, use the get function with no output arguments.

get(da)

  General Settings:
    EventLog = []
    EventLogMax = 1000
    Group = [1x2 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

To obtain a specific property, pass that property name to the get function.

clientName = get(da,'Name')

clientName =
localhost/Matrikon.OPC.Simulation.1

You can get information about a property using the propinfo function. Information includes whether the property is read only, and valid property values for properties that have a predefined set of values.

statusInfo = propinfo(da, 'Status')

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

To set the value of a property, use the set function.

set(da, 'Timeout', 30)

Step 6: Clean Up

When you are finished using OPC Toolbox objects, you should delete them from the OPC Toolbox engine. Deleting the client object deletes the group and item objects associated with that client.

disconnect(da)
delete(da)
clear da grp1 grp2 itm1 itm2 itmVec