Opcclient
Purpose
Creates an opcclient object which allows access to OPC servers.
Synopsis
- code here
Description
The opcclient object allows the Matlab user to connect to an OPC DA server and read item values from or write item values to the server. Opcclient is available in PLS_Toolbox Version 7.3 and later and provides access to OPC servers supporting OPC Data Access standard v2.05a.
Simple example of accessing item values on an OPC server on the same machine as the opcclient System Set-up 1. Start an OPC server on your computer. Free demo OPC servers are available from Matrikon or Graybox, and others.. 2. Ensure computer is configured for DCOM communication. See, for example, http://www.opssys.com/InstantKB/article.aspx?id=10834, or http://cache.automation.siemens.com/dnl/zY/zYwMjc3AAAA_31198863_FAQ/OPC_via_DCOM_e.pdf 3. Create a user with admin privileges, for example, "testuser", with example password "test", or use any user with admin privileges and with an account password. It may be necessary to cycle the Windows firewall off and back on after performing steps 2 and 3. 4. Find your computer's IP address. Get it from the "IPv4 address" entry in the results from the "ipconfig" command.
Notes: 1. You need to know the Program ID of the OPC server you want to connect with. The Program ID is a human readable form of the server's COM unique identification, its Globally Unique Identifier (GUID). Graybox's progID is 'Graybox.Simulator'. 2. You will need to know the names of any items you want to access on the server. Item names (or tags) are usually in a hierarchical namespace specific to a server. Matrikon example: Bucket Brigade.ArrayOfReal8, Graybox example: numeric.saw.float.
Details: Opcclient is implemented using the Java-based openscada.org Utgard package. OPC DA communication is based on the Windows COM protocol.
Simplifications 1. Uses default group only. 2. Item types on Matlab side are simply doubles, rather than mapping to int8, int32, float32, double 3. Only tested on local computer which is protected by firewall. Security issues would exist if the OPC server is on a remote computer because of sending user login and password info to the OPC server computer
Inputs
- first = first input is this.
Optional Inputs
- second = optional second input is this.
Outputs
- firstout = first output is this.
Options
options = a structure array with the following fields:
- plots: [ {'none'} | 'final' ] governs plotting of results, and
- order: positive integer for polynomial order {default = 1}.
Example
% Create client instance
client = opcclient(1);
% Connect to OPC Server
% client.connect(IPaddress, domain, username, password, OPC_server_progID);
client.connect('10.0.2.15', 'localhost', 'testuser', 'test', 'Matrikon.OPC.Simulation');
% Reading a single item
%Read the specified OPC item. The function returns a (value, quality, timestamp) tuple. If the call fails, the quality will be set to 'Error'.
itemname = 'Bucket Brigade.Int4'; % This server item tag, is read/write
[value timestamp quality] = client.read(itemname);
% Writing a single item
newvalue = 23;
res = client.write(itemname, newvalue);
% And read its value back
[value timestamp quality] = client.read(itemname);
% Writing an array item
itemname = 'Random.ArrayOfReal8';
newvalue = rand(6,1)*10;
res = client.write(itemname, newvalue);
% And read its value back
[value timestamp quality] = client.read(itemname);