Code

	The code for this and other example scripts can be found in the DataHub distribution archive, typically at this location: C:\Program Files\Cogent\Cogent DataHub\scripts\ Please refer to Section 3.1, “How to Run a Script” for more information on using scripts.

/* This script requests a reload of data from a connected OPC DA 
 * server without disconnecting from the server.  It is particularly 
 * useful for automatically adding new points, and can poll for new 
 * points based on a timer or on a trigger point.
 *
 * You will need to edit the following three variables to run the
 * script on your system:
 *
 *  connection_label: The name given to your OPC DA connection when 
 *                    you defined your OPC server.  This appears in 
 *                    the "Connection" column in your list of OPC 
 *                    Client connections in the Properties window.
 *
 *  poll_time:   The poll rate to check for new points, in seconds.
 *
 *  trigger_point:  The name of the point you will use as a trigger.
 *
 */ 

require ("Application");
require ("OPCSupport");

class OPCReload Application
{
    connection_label = "OPC002";  // connection label in "Connection"
                                  // column of OPC properties
    poll_time = 30;               // poll rate for new points,
                                  // in seconds
    trigger_point = #$domain_name:point_name;  // name of point
                                               // used as a trigger
}

/* Transmit a "reload" command to the server, without disconnecting.
 * To disconnect and reload, change the paramter to opc.reload to t
 * instead of nil.
 */
method OPCReload.reload ()
{
    local   opc = new OPCConnection();
    opc.setVerbose(t);
    opc.setServer(.connection_label);
    opc.reload(nil);
}

/* Start the polling timer */
method OPCReload.constructor ()
{
    // To poll for new points periodically, use this line
    .TimerEvery (.poll_time, `(@self).reload());
	
    // To poll for new points only when a specific data point changes,
    // use this line
    .OnChange (.trigger_point, `(@self).reload());
}

/* Instantiate the class.  This calls the constructor. */
ApplicationSingleton (OPCReload);