The DANVOP controls have built-in OPC server access support and minimize the amount of code needed for a user specific application. Many applications can be created without even writing a single line of code.

The controls visualize current OPC server data and write data to the OPC server based on user action. Controls such as buttons, check boxes, numeric up/downs write pre-configured data to the OPC server. More complex user input has to be validated and handled in user added code. 

The OPC DA server access bases on the features offered by the OPCDA.NET client component. A license of the OPCDA.NET client component V4.3 or newer is required as the base for DANVOP.

The OPC server access code built into the controls bases mainly on the DataBind and asynchronous Write methods. The user added code has all OPCDA.NET features available to handle any application specific server access requirements.
The OPC server access implemented within the DANVOP controls is very robust with error detection, reporting and recovery. The application developer can take advantage of these features by doing additionally needed server access through DANVOP controls.

A license of the OPCDA.NET client component V4.3 or newer is required.

Following is an overview of the DANVOP controls with samples of some of the possible variants and a short description of the features.

Bar
Bars visualize an item value in a wide variety of shapes and colors. Control properties define the shape and color of the bar and lower and upper value of the control. The bar control can be bound to any OPC item with a numeric value.

LED
LED controls visualize On/Off states. Usually Boolean item values are assigned. For increased flexibility it’s possible to bind items with any type of numerical value and an on/off limit value can be specified. Item values < limit are displayed as OFF.

Label
The Label control offers all features of the .NET label control and has additional properties to bind the control to an OPC item. The item value is converted to a string and is displayed between an optional prefix and suffix.

TextBox
TextBoxes can be single of multi-line. OPC item values are displayed between an optional prefix and suffix. In multi-line boxes a prefix and suffix may be defined for each line. OPC item array values are displayed with each element on a line, between the optionally defined prefix and suffix.

Application code is required to use the text box as a user input control. The application code has to validate the entered data and write the data to the OPC server using the vopAsyncWrite control or other OPCDA.NET server access methods.

ListBox
Simple and array OPC item values can be associated to be displayed at/from the defined line.

ListView
The ListView control is used in ‘Detail’ display mode to show array values in either rows or columns.

Analog Meter
The Analog Meter control has a definable range and shows the current value on one OPC item.

Trend Chart
Trend charts display the recent values of the associated OPC item as lines. Up to four items can be displayed in one chart.

CheckBox
The CheckBox control is supported as an input and output control. It can be displayed in form of a checkbox or button. Up to three OPC items can be assigned. If the ‘display’ item is assigned then the ‘check’ state is shown according the current OPC item value. As a user input control state changes are written to the OPC server. A definable value is written to either one two different items depending on the new control check state.

Radio Button
The Radio button is a user input control that is used in groups. Only one radio button in the group is in checked state.

Each radio button writes a definable value to either one two different items depending on the new control check state.

Button
The button control writes the defined value to the associated OPC item on each click. Optionally a ‘step’ value can be defined. It causes with each click the value to be incremented/decremented within the defined limits. Button controls are usually used in pairs to alternate or increment/decrement values.

Slider
The slider control has a min/max range and writes the current position value to the OPC server on each movement.

Numeric Up/Down
The numeric up/down control has a min/max range and step value. On each up/down click the new value is written to the associated OPC server item. The value can also be edited. Edited values are shown in the ‘edit’ color until ‘enter’ is clicked to write the new value to the OPC server.

OPC Browse Tree
The associated OPC server is browsed when the ‘browse’ button is clicked or a branch is selected for the first time.
Application code is required to handle the browse result.

Asynchronous Write
This is an invisible control that supports writing data to OPC server items using. Data assigned to the ‘Value’ property is written to the defined OPC item.
The control is associated with an OPC DataBind control and uses its OPC server connection to write data asynchronously and supervise the successful operation.

OPC Error Handler
An error handler control can be associated with an OPC server control. Errors in the OPC server access are listed in the log window, in read until acknowledge.

OPC Server Control
An OPC server control is required for each accessed OPC server. Multiple forms can use the same OPC server control. |
This control can either be shown to document the accessed OPC server and it’s current status, or the control can be hidden.
The server connection is periodically checked in a background thread and each asynchronous server access is time limit checked.
Properties define the error handling. Errors can be shown as pop-ups, listed in an error handler control or logged into a log file.

OPC DataBind Control
This is an invisible control. At least one is required per form. Multiple DataBind controls can be used to handle the server access with e.g. different update rates. The DataBind control is associated with an OPC server control and each DANVop control is associated with a DataBind control.

Simple sample structure.