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Keystrokes Mode and DDE Mode

A comparison between the two main modes of WinWedge: Keystrokes Mode and DDE Server Mode

WinWedge can be configured to send data to other Windows programs either by coinverting the data to "keystrokes" or by passing the data using DDE. The primary advantage of setting up the Wedge to send keystrokes to another application rather than passing data using DDE is simplicity. By sending keystrokes, no special programming is required in the application that will receive the data. For example, when reading data into a spreadsheet, a common requirement is to have successive readings from a device appear in a column in the spreadsheet. By sending keystrokes you could simply configure the Wedge to send a "Down Arrow" keystroke after each input from your device to move the cursor down one cell and thus be ready for the next input.

A minor disadvantage of sending keystrokes is that the application that is receiving the data must be in the foreground and have the input focus before the Wedge can send any keystrokes to it, thus true background processing is not possible when sending keystrokes.

Sending keystrokes from one application to another is also slightly slower than using DDE.

DDE on the other hand does not require the receiving application to have the input focus therefore all data transfers can occur in the background while you work with other programs in the foreground. One difficulty with DDE is that "linked "data from the Wedge (or any other DDE Server) is always transferred to the same location in the client application (i.e. a "linked" cell in a spreadsheet). To get successive data readings into a column in a spreadsheet you must write a macro in the spreadsheet that runs automatically after each input is received. The purpose of the macro would be to either explicitly request the data from the Wedge or copy each new data item from a linked cell and paste it to the bottom of the column in your spreadsheet. One way to accomplish this is to have WinWedge issue a DDE Command after each input that causes the spreadsheet to run a macro that either requests the data or copies any linked DDE data into a column.

A powerful feature of DDE is that applications that support it can send commands directly to each other and thus you could fully automate a data collection process between your application program and WinWedge. This requires a small amount of programming in your application but the extra effort allows you to create extremely sophisticated device interfaces. Also, because all DDE operations can occur in the background, even with a minimized application, DDE operations typically execute much faster than sending keystrokes from one application to another.

Note: WinWedge does not have to be in "DDE Server Mode" in order to accept and process DDE commands. WinWedge will still execute any DDE commands sent to it even if it is in "Send Keystrokes Mode" or "Log To Disk Mode".


Categories: Powerful Automation (DDE)

Last Updated: 2013.08.28

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