Internal data points of the OPC HDA Client

_OPCHDA

For each OPC HDA client a data point _OPCHDA<ManagerNumber> of this type must exist.

Data point element Type Description
Config.Servers dyn_string List of data points of type _OPCHDAServer to which the OPC HDA client establishes a connection. The OPC HDA client detects changes to this data point element at runtime. Therefore no restart is necessary.

_OPCHDAServer

For data mapping the OPC HDA client uses this internal data point type. A data point of this type must exist for each OPC HDA server to which the client shall be connected.

Data point element Type Description
Config.ConnInfo string

Defines the ProgID in the following format: <hostname>/<COM object>

This defines how the server can be accessed.
State.VendorInfo string Vendor specific information
State.MajorVersion uint Major version number
State.MinorVersion uint Minor version number
State.BuildNumber uint Build number
State.StartTime time Time when the server was last started
State.ServerState uint Current server status
State.MaxReturnValues uint Maximum number of values the server can return per item. A value of 0 indicates that the server forces no limit on the number of values it can return.
State.ServerStateText string An optional string explaining the server status
State.LastUpdateTime time Time when the server status was last updated
Browse.GetBranch dyn_string

This element triggers the browse request. Following parameters must be defined:

Parameter Description
requestId Unique request ID
startNode Defines the start position for browsing. If the first level shall be browsed an empty string must be used.
browseType

Defines the browse type. Following types are available:

Value Description
1 Returns all branches under the defined start node
2 Returns all leaves under the defined start node
3 Returns the whole server structure, i.e. all items along with the path. In this case an empty string must be used for the startNode parameter.
Browse.BranchNames dyn_string The browse result (branch names) is displayed here.
Browse.BranchIds dyn_string The browse result (branch IDs) is displayed here.
Command.HistoryRead dyn_string

A historical query is started via this element. Following parameters must be defined:

Parameter Description
requestId Unique request ID
itemDescr Path or item which shall be queried
start Start time
end End time
valueCount Number of queried values
withBounds With or without boundary values, refer to the OPC HDA 1.20 specification for further information.
respDP Response data point

_OPCHDAHistoryReadResponse

The result of historical queries is written to response data points of this type.

Data point element Type Description
RequestId string To identify to which request the result belongs.
Timestamps dyn_time Timestamps of the queried values
DataValues dyn_string Values queried from the OPC HDA server
ValueStatusCodes dyn_bit32 Quality information of the queried values
ReturnCode int

Return value of the query. Following values are possible:

Value Description
0 Query successful
-2 No connection to the server
-3 Problems when requesting a server handle
-4 Error reading the data
-5 Not enough parameters defined (at least two of the parameters StartTime, EndTime and Number of Values must be defined)
-6 Server returns an error for this query
DataType string

Data type of the queried item. Following data types are supported:

  • VT_BOOL

  • VT_I4

  • VT_UI4

  • VT_R8

  • VT_UI4

  • VT_DATE