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Workbench for Windows: DDE Output from WorkBench PC for Windows into Microsoft Excel

An important feature of WorkBench PC for Windows is its support of Dynamic Data Exchange (DDE). Utilizing the DDE Output and DDE Input modules, users have the ability to send and receive data between WorkBench and other Windows applications. These modules can then be connected to other modules to incorporate the data into the worksheet.

One of the most common uses of DDE in WorkBench is to send collected data to a spreadsheet for further analysis. As a simple example, suppose you want to output the data from a Generator module into a Microsoft Excel worksheet. The following steps show how to do this:

  1. Load WorkBench. Create a Generator module and a DDE Output module on a new worksheet.
  2. Click on the A/D button in the function bar, or choose Experiment Setup from the Menu. Set the Block Size to 8 and the Sampling Rate/Channel to 50Hz. Close the dialog box.
  3. Double-click on the DDE Output module to set its parameters. For this Excel example, set the parameters as follows:
    • Application: Excel
    • Topic: WBfWdde.xls (or your worksheet name. Remember to include the ".xls" extension.)
    • Item: DDECELL
    • Output Format: Columns
    • Separator: Tab
    • Final Character: CR LF
    • Decimal Format: Point
  4. Double-click on the Generator module. Check that the defaults are set to Sine Wave "10 Hz" and Amplitude "4" then click OK.
  5. Open Excel, creating a new worksheet. Select cells A1 through A8. Note that the number of columns matches the number of channels being passed through DDE, one in this case. The number of rows selected should always equal the Block Size, 8 samples for our example.
  6. Use the Insert/Name/Define (or Formula/Define Name in older versions) menu selection in Excel to name the selected area. The name should be the same as that entered in Item field of the DDE Output module, "DDECELL" for our example.
  7. Save the worksheet as "WBfWDDE.xls" (or the name you specified as Topic in WorkBench).
  8. Return to WorkBench and start the experiment. The Excel column should immediately begin to show the acquired data in real-time.

NOTE: For a better display of this real-time data, use cells A1 through A8 as the data series for a chart in Excel. In this way, a graph of a moving sine wave will be displayed. For better resolution of this sine wave, increase the Block Size and Sample Rate in WorkBench and make the associated changes in Excel.

If the Application or Topic is incorrectly entered in WorkBench, then a "Cannot Create DDE-Link" will be displayed. It is important to make sure that the ".xls" ending is present in Topic or this same error message will result. An incorrect Item will not cause an error message but will result in no information being transferred to Excel.

To transfer multiple columns of data to Excel, use one DDE Output module with multiple channels. For example, if two columns of data are needed in Excel, then the DDE module would have two channels selected. The Application, Topic, and Item settings are the same for all channels. All that needs to be changed is the block selection in Excel - select two columns of 8 rows and define the name as DDECELL. When WorkBench is started each channel on the DDE output icon will pass data to one column in Excel.

DDE transfer of data allows data to be passed from one application to another in the Windows environment. Typically, any new data passed to the receiving application will write over any preceding data, rather than append it. In this way, data sent to Excel will overwrite the previous "blcok" of data to have been sent from WorkBench. If it is required for all data to be present in Excel at the end of an experiment, it is necessary to log data to disk using the Write module in WorkBench, and then to open that file into Excel. This is a limitation with DDE, not WorkBench PC for Windows.

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