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Example Code
Code and Documents
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Overview
This document provides information about how to develop powerfull, full featured OPC DA 2.X/3.0 client application on LabVIEW. The method uses OPC core components binaries (which are available for free at http://opcfoundation.org/) as a low level interface to perform all tasks. For the most of OPC features wrapper VIs exist and grouped as a standard LabVIEW libraries and classes. Upon installation logically grouped VIs will apear in functions palette. All binary dependencies will be automatically installed into <GAC> directory after packege installation.
Please refer to http://opc-da.com/ for more information.
Description
OPC DA API initiate and control communications with OPC Servers. The toolkit is meant for translate LabVIEW freindly application requests into an OPC equivalent request and send it to the appropriate OPC Server for processing. In turn, when OPC data returns from the OPC Server, the toolkit translates it back into the LabVIEW native format so the application can properly work with the data.
You can use OPC DA API in any LabVIEW application to enable it to communicate with any compliant OPC Server visible to it on the network. The intuitive implementation of toolkit makes it irreplaceable solution for creating applications such as HMIs, trending packages, historians, report writers, etc.
Using OPC DA API you can communicate with multiple OPC Servers at the same time. Effectively, this means an OPC Client can read and write data to and from multiple data sources via their respective OPC Servers. Connect as many OPC servers as you needs to just by calling appropriate wrapper VI with correct settings.
The OPC DA API covers the most of OPC specification, such as:
1. Browse Network
2. Browse Computer’s OPC Servers List
3. Connect to OPC Server
4. Browse OPC Server
5. Create OPC Groups
6. Add Items Into Group
7. Synchronous and asynchronous read and write
8. Remove Items from Group
9. Remove OPC Groups
10. Disconnect from OPC Server
11. Accses OPC Item properties
12. Accses OPC Group properties
13. Accses OPC server properties
14. Accses OPC server status
For detailed documentation of OPC DA API please refer to http://opc-da.com/Documentation.html
For FAQ about OPC DA API please refer to http://opc-da.com/FAQ.html
Steps to Implement or Execute Code
- Download the OPC DA API from http://opc-da.com/toolkits/opc_support_lib_opc_da_api-1.1.0.24.vip
- Download the simple OPC client example which is using OPC DA API from http://opc-da.com/resources/OPC-DA_Example.zip (starting from ver. 1.1.0.24 example VI's are included into installation package)
- Run the "opcda_simply_client_example.vi"
- Click on the "Browse Network". The client application will browse local network. Choose one of local network computers where OPC server is running from listbox.
- Select specification. Use eiather 2.X or 3.0.
- Click on "Browse Computer". The client application will show all running OPC servers on selected machine. Choose one of the OPC servers from listbox.
- Click on "Connect". The client application wil automatically browse the root folder of selected OPC server and populate it on "Browser".
- Double click on tags folder in "Browser" to navigate into it.
- Read or write tag value.
Requirements
Software
LabVIEW 2015 Base, Full, or Professional Development System.
.NET Framework >= 4.5.
Hardware
Additional Images or Video
Benchmarking
Here is the benchmarking of how fast the OPC DA API can work.
As you can see, as big your tag set that you wish to read as fast it will be performed. In this example we read all data types: String, Boolean, Double, Float, U8-U32, I8-I32, Array.
A 20 % of tag quantity were array at list with 5 elements.
MS Windows Security Configuration
If you wish to connect to OPC server within local network you need configure DCOM security settings first. The easiest way to do this is explained here.
Application distribution which uses LabVIEW OPC DA API
Upon creating distributive application (.exe) from LabVIEW code, which uses LabVIEW OPC DA API you have to download and include the OPC DA 3.00 Binaries installer to your application installer (or install it manually on the machine which will run the application) in order to guarantee proper work of the application.
Example code from the Example Code Exchange in the NI Community is licensed with the MIT license.
