How to set OPC Server update rates with DataSocket

[Geoff Love]

I'm using LabView datasockets to read data from an OPC Server. Is there a way I can set the OPC Group update rate and deadband? It appears datasocket automatically sets these to 100 mS and 0.0 respectively by default.

[Zvezdana S.]

Geoff,
The "ms timeout" on the DataSocket Read VI specifies how long to wait for a value update. Default is 10s.
What update rate can I get from DataSocket communicating with an OPC server?
http://zone.ni.com/devzone/conceptd.nsf/2d17d611efb58b22862567a9006ffe76/b58c6ca2be2b99da862569880076e168?OpenDocument
The deadband is a part of the client configuration but not the server configuration. Refer to the documentation for the client for more details.
You can use the following protocols when you publish or subscribe to data using DataSocket:

� DataSocket Transport Protocol (dstp)�The native protocol for DataSocket connections. When you use this protocol, the VI communicates with the DataSocket server. You must provide a named tag for the data, which is appended to the URL. The DataSocket connection uses the named tag to address a particular data item on a DataSocket server. To use this protocol, you must run a DataSocket server.

� Windows OLE for Process Control (opc) �Designed specifically for sharing real-time production data, such as data generated by industrial automation operations. To use this protocol, you must run an OPC server.

� Windows logos�An internal National Instruments technology for transmitting data between the network and your local computer.

� File Transfer Protocol (ftp) �You can use this protocol to specify a file from which to read data.

� file�You can use this protocol to provide a link to a local or network file that contains data.

The following table shows examples of each protocol URL.

URL Example
dstp dstp://servername.com/numericdata, where numericdata is the named tag
opc opc:\National Instruments.OPCTest\item1opc:\\machine\National Instruments.OPCModbus\Modbus Demo Box.4:0opc:\\machine\ National Instruments.OPCModbus\Modbus Demo Box.4:0?updaterate=100&deadband=0.7
logos logos://computer_name/process/data_item_name
ftp ftp://ftp.natinst.com/datasocket/ping.wav
file file:ping.wavfile:c:\mydata\ping.wavfile:\\machine\mydata\ping.wav
Use the dstp, opc, and logos URLs to share live data because these protocols can update remote and local controls and indicators. Use the ftp and file URLs to read data from files because these protocols cannot update remote and local controls and indicators.
Refer to the DataSocket Examples for examples of using DataSocket connections.
DataSocket (implementation) can use any of these protocols - It'll use the one that you tell it to use by the header of the URL (dstp: or opc: logos: etc). All these protocols are isolated and don't depend on each other. In other words DataSocket (implementation) has embedded clients for all these protocols and will use the specified by the URL.

Zvezdana S.
National Instruments