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Visual Basic for Applications Serial Port Software Example

Visual Basic is used for many control applications, from simple communications, to elaborate test equipment with user control or automated.  But many people don't realize that Visual Basic for Applications which is built into many MS software programs such as Word, Excel, Publisher, Access, and even the Front Page editor I'm using right now, can be used for control applications.

New item If you need to control our relay boards, but do not have any programming experience you now have an option.  Our relay boards can now be controlled directly from a desktop shortcut using our command-line software. This eliminates having to deal with the mscomm32.ocx driver!

For example, you can be in Access or Excel, start a macro that would power up an external data acquisition unit and receive data into the software utilizing VBA, serial control, and one of our serial relay boards.  You could control room lighting, or any other device that you would like to turn ON or OFF from within a application, just think of the many possibilities. 

Visual Basic for Applications has many of Visual Basic's commands and controls, that can be utilized for control applications.  We will show you how to use this powerful application to control our serial relay boards.

Note: this example is tailored to the first time Visual Basic for Applications user, but the information is useful for the advanced user that is unfamiliar with serial port control.  Click here if you're familiar with VBA and want to jump directly to the code segment.

Let's get started:
For this demonstration we will use Excel's VBA editor, but any of the software that has built in VBA support will work.  Start Excel and select >> Tools >> Macro >> Visual Basic Editor, from the pull down menus as shown in the picture below, or use Alt+F11 shortcut.

Depending on which version of Excel you are using, this and the following screen may look different.  The Visual Basic Editor will appear as shown below.

After VBA is loaded Right Click in the project window, Select >> Insert >> Userform and a blank form will be loaded, with a control tool box as shown below.

Now we are going to add serial port control to the control box so that we may use it in our application.  For this demonstration we are going to use the mscomm32.ocx communication driver, depending on what other MS applications you have loaded on your system, this driver may or may not be available on your system.

Right click in the controls box and select >> Additional Controls… Scroll down to you see Microsoft Communications Control, and click on the check box on the left, as shown below.

If you don't see this driver available in the additional controls window you can do a file search using windows Start >> Find >> File or Folder to search for mscomm32.ocx.  If this file is found you need to copy this file into the  c:\windows\system directory so the VBA can find it.  If this driver is not found click here to continue.

Click OK to continue.  The control box will now have an icon of a telephone sitting on a modem displayed in the controls window as shown below.

Select this control and place your cursor on the user form, click the left button and the control will be placed on the screen. If you see a warning like shown in the picture below you either have a unlicensed copy of the control or the control is not licensed properly.

If you downloaded the mscomm32.ocx driver from the internet and you don't have Visual Basic, Visual Fox, or one of the other programs that it is supplied with, you don't have a registered copy and will not be able to use this driver. Don't worry, there are two other ways to accomplish serial communications that don't require this driver, click here for the other two options.

Click on the command button icon in the tool box (rectangular box) and place two buttons on the user form. Click on CommandButton1 and the options will appear in the properties window. Click to the right of the Caption in the properties window and change commandButton1 to "All Relays ON".  Click on the commandButton2 or select this name from the pull down at the top of the properties window, and change this to read "All Relays OFF" as shown in the picture below.

Click on the MScomm icon or use the properties pull down menu to view the properties for this control as shown below.

Click on the property labeled RThreshold, change this value from a "0" to a "1".  Do the same for the SThreshold property.  Everything else in this window can remain the same for this example.

Note: If you need to read the port status on the board (which is not shown in this example) you need to change the InputMode property to  "1-comInputModeBinary" by selecting the right pull down.

We are now finished with the configuration of the serial port and command buttons.  The default settings are already set for com port 1, 9600 baud, 8 bits, no parity, and one stop bit.

From the menu at the top of the Visual Basic for Applications screen select View >> Code or press F7, and a code window will be displayed where the form currently resides.  Click in the following box and select the contents of the box by holding the left mouse button and dragging down over the contents.  Hold the Ctrl Button down and press "C'' to copy the contents to the clipboard.

Switch to Visual Basic for Applications and click inside the code window and press Ctrl "V" to paste the contents, the window should now look like the following picture.

That's all the code that is required to turn all the relays ON and OFF on our relay boards, it will work on the 1, 2 & 8 Channel relay boards.  Select File >> Save Book1 from the pull down menu to save your project before you attempt to run the program.

All that's left to do is run our program, but first make sure the relay board is connected to com1 on the the back of your computer using the 9 pin serial to modular cable adapter.  Connect the modular cable from the adapter to the input of the relay board.  Plug the wall transformer cable into the board and the wall transformer into the wall receptacle or apply power to the board if your using the internal transformer version.

Assuming that everything is connected up properly, press the blue right arrow at the top of the screen and our program will run.  To stop the program press the blue square box to the right.  The running program is shown below.

 Click the "All Relays ON" button and you will hear an audible click from the relays that is turning them ON and pressing the "All Relays OFF" button will turn them OFF.

Congratulations on your first Visual Basic For Applications control program!  We're sure you will find many practical applications for your RS232 serial controlled relay board.

If you have any other questions you may contact the support dept at or you may request information using our feedback form.

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