Methods

Setup OPC Server connections and items.

The Setup method is used to setup the connection to the needed OPC Servers and the needed OPC Items. It is possible to setup a connection to any number of local and remote OPC Servers and any number of OPC Items.

The list of OPC Items will be presented to the script as a flat list where only the given name of each item is used, no matter which and how many different servers are used.

The list of servers is configured under the SERVERS section in the General tab of the properties.

A new server can be added by pressing the ‘Add server’ button of the SERVERS heading line.
An existing server connection can be removed by pressing the Delete key when the server line is selected.
A server connection can be moved up and down in the list by pressing Alt + Up or Alt + Down when the server line is selected.

There are three fields to setup for each connected OPC server:

• ServerIDThis is a text field where the user must set a descriptive short name for the server. This name is used in the item configurations to identify the parent server of each item.
• MachineNameThis is a text field for the name of the OPC server machine. It can be the machine name, the machine IP address or empty when connecting to a local OPC server.

Please note that this means that there is a difference between connecting to localhost (which involves DCOM) and connecting to the local OPC server by setting the MachineName to the empty string. Please see the section named Troubleshooting OPC problems for more.

• ServerClassThis is a text field for the class name of the OPC server on the specified machine. Click the browse-symbol (…) or press the space button to open a dialog for browsing available server classes on the selected machine.

The list of used OPC items is configured under the ITEMS section in the General tab of the properties.

A new item can be added by pressing the ‘Add item’ button of the ITEMS heading line or by pressing the Enter key on the line where you wish to insert a new item.
An existing item can be removed by pressing the Delete key when the item line is selected.
An item line can be moved up and down in the list by pressing Alt + Up or Alt + Down when the item line is selected.

The different fields for each item are:

• ServerIDThis is a text field where the parent server of the item is selected. The field must be set to the server ID of one of the servers configured in the servers list above.
• NameThis is a text field where the chosen name of the item is set. By default the name will be set to the name of the selected OPC item, but it can be set to a more descriptive name, making the scripts more readable and easy to maintain.
• ItemIDThis field is used to select the OPC item to use. Click the browse-symbol (…) or press the space button to open a dialog for browsing the server for available items.
• TypeThis field is for selecting the resulting data type of the item in SeqZap. The field will be set automatically when selecting the item via the item browser dialog.
• DirectionThis field shows the data access direction for the item; whether it is read-only, write-only or read-write.
• DescriptionThis is a text field where the item can be given a short description.

Many different errors can occur in the setup process. The different error types are listed below along with a description of how each error type is handled during setup.

Errors on server entries:

Error description	In parser	Breaks setup
Missing ‘Server ID’ The ‘Server ID’ field is empty.	Error	Yes
Missing ‘Server Class’ The ‘Server Class’ field is empty.	Error	Yes
Duplicate ‘Server ID’ on server entry The ID has the same name as a pervious entry in the list.	Error	Yes
The specified ‘Server Class’ was not found The specified server class was not found on the specified machine.	No	No

Errors on OPC items:

Error description	In parser	Breaks setup	Step error	Simulates
Missing ‘Server ID’ The ‘Server ID’ field is empty.	Error	Yes	Yes	No
Unknown server ID No server entry has the specified server ID.	Error	Yes	Yes	No
Missing ‘Name’ The ‘Name’ field is empty.	Error	Yes	-	No
Duplicate ‘Name’ The entry has the same name as a previous entry in the list.	Error	Yes	No	No
Missing ‘Item ID’ The ‘Item ID’ field is empty.	Error	Yes	Yes	No
Unknown item ID The OPC server has no item with the specified ID.	Warning	No	Yes	No
Selected ‘Type’ is different from the data type of the item on the OPC server.	-	No	No	Yes
Selected ‘Direction’ is incompatible with the direction of the item on the OPC server.	-	No	No	Yes
Syntax error in specified ‘Update Rate’ The specified update rate does not follow the supported format of a time interval value.	Error	Yes	No	No
Quality is bad and not one of these values: LastKnown, WaitingForInitialData	-	No	No	Yes

The column ‘In Parser’ indicates whether the error is listed in the Errors and Warnings view, and whether it is reported as an error or as a warning.
The column ‘Breaks setup’ indicates whether the error will prevent the setup of the tool from completing. If the error breaks the setup, the error has to be fixed before the tool can be used.
The column ‘Step error’ indicates whether steps using the item will report an error in the Errors and Warnings view.
The ‘Simulates’ column indicates whether the error will force the tool into ‘Simulate’ mode.

Gets the value for the specified OPC item.

This method gets the value of an OPC item.

The setup shows the list of available items for the selected OPC Client instance. The user can select one of the items on the list and the output data type of the procedure step will be set to the data type of the selected item.

Sets the value for the specified OPC item.

This method sets the value of an OPC item.

The setup shows the list of available items for the selected OPC Client instance. The user can select one of the items on the list and the input data type of the procedure step will be set to the data type of the selected item.