www.gusucode.com > opc 案例源码 matlab代码程序 > opc/opcdemo_hda_browsing.m
%% Locate and Browse OPC Historical Data Access Servers % This example shows how to use the OPC Toolbox(TM) to browse the % network for OPC Historical Data Access servers, and use OPC Toolbox functions to query the % server name space for server items and their properties. % % *PREREQUISITES:* % % * <docid:opc_examples.example-ex84291595> % Copyright 2004-2014 The MathWorks, Inc. % $Revision: 1.1.6.3 $ $Date: 2013/03/26 00:40:56 $ %% Step 1: Browse the Network for OPC HDA Servers % You use the |opchdaserverinfo| function to query a host on the network for % available OPC Historical Data Access servers. This example uses the local host. hostInfo = opchdaserverinfo('localhost') %% % Find the server info entry with a description starting with Matrikon. hIndex = findDescription(hostInfo,'Matrikon') hostInfo(hIndex) %% Step 2: Construct a Client Object and Connect to the Server % Use the |ServerInfo| object returned in the previous step to construct a client object. hdaObj = opchda(hostInfo(hIndex)); %% % You can also specify the host name and server ID directly. hdaObj = opchda('localhost','Matrikon.OPC.Simulation.1') %% % Connect the client to the server. connect(hdaObj); %% Step 3: Retrieve the Server Name Space % Retrieve the name space of the server. ns = getNameSpace(hdaObj) %% % Each element of the structure is a node in the server name space. ns(1) %% Step 4: Find Items in the Name Space % Use the |serveritems| function to find all items in the name space containing the string |Real|. realItems = serveritems(ns,'*Real*') %% Step 5: Query Server Item Attributes % Examine the current normal maximum value of the tenth item found. maxVal = readItemAttributes(hdaObj,realItems{10},hdaObj.ItemAttributes.NORMAL_MAXIMUM,now,now) %% % The warning indicates that the item has not yet been stored in the historian database, but the % preconfigured item attributes are being returned. %% Step 6: Clean Up OPC Toolbox Objects % Disconnect the client from the server and remove OPC Toolbox objects from memory when you no % longer need them. Deleting the client object also deletes the group and item objects. disconnect(hdaObj) delete(hdaObj)