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Programming W.A.S.P. in Visual Basic |
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Although WASP comes with it's own software (WaspWare) to allow the beginner to start using it in home automation projects very quickly, it also comes with a DLL interface to allow the intermediate and advanced user to write their own programs for it. The DLL provides a general purpose interface that greatly simplifies the task of writing programs for a USB device. It can be tricky manipulating the USB comms into sending and receiving messages to and from a device which can easily be plugged and unplugged at any time. The DLL eliminates all of these headaches by simplifying the task into three library functions. |
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| InitWasp( ) , SetOutputs (outputs) and ReadInputs(analogue) | |||||||||
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InitWasp()
is called somewhere near the start of your program and takes care of all
of the USB comms initialisation and prepares the WASP for sending and
receiving messages. |
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SetOutputs (7) |
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| and the following would turn on outputs 1, 2, and 4 | |||||||||
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SetOutputs (11) |
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ReadInputs(analogue) can also be called at any time during your program to read the current values of the analogue inputs. When you call this function the WASP performs an analogue to digital conversion on the 4 inputs and stores the results in 4 (32 bit) integers. The integers are actually the elements of the array called analogue. This array has been passed By Reference to the wasp dll by your program, allowing the dll to modify its contents directly. You array should be declared as follows... |
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| Dim analogue(4) As Integer | |||||||||
| The values stored in these array elements will correspond to the analogue inputs representing 0 to 5volts as 0 to 255. For example if the analogue inputs are 1v, 2.5v, 4v and 5v respectively the contents of the array analogue after the ReadInputs( analogue(0) ) function call will be.... | |||||||||
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analogue(0) = 51, analogue(1)=128, analogue(2)=204 and analogue(3)=255 |
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The only other thing that a VB program must do is to declare the functions that it is going to use within the DLL and the name of the DLL itself. This must be done at the start of your program or at least before any references to the two functions are made. The following is a program excerpt showing how this is done... |
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Declare
Function
InitWasp Lib "wsp.dll"
() As
Boolean Declare Function SetOutputs Lib "wsp.dll" (ByVal outputs As Integer) As Integer Declare Function ReadInputs Lib "wsp.dll" (ByRef analogue As Integer) As Integer |
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The first declaration states that the function InitWasp has no parameters, is found in wsp.dll and returns a boolean value. The second states that SetOutputs has one integer parameter passed by value rather than reference, is found in wsp.dll and also returns an integer value. The third declaration states that ReadInputs has one parameter which is a reference to an integer and returns an integer value. The reference to the integer is actually the reference to the first integer in an integer array, with the subsequent 3 array values also being used to store analogue results. It should be noted that the |
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Lib "wsp.dll" |
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lets the program know where to find the wsp.dll file. When written like this it assumes, since there is no path information, that the wsp.dll file can be found in the windows system directory c:\windows\system32 If you like you can copy the file wsp.dll on the installation disk to the system32 directory and the above statement will work perfectly. Alternatively you can copy the file to some other location and give that location in the declaration as in the example below... |
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| Declare Function InitWasp Lib "c:\mylibrary\wsp.dll" () As Boolean | |||||||||
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© Copyright pc-control.co.uk 2008 |
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To speed up your development of software for the WASP a complete working
example is available for download below. It is called VBwasp and creates a
very simple form based program that has individual buttons for various
functions such as initialising the WASP and setting various patterns on
the outputs. The main (and only) screen is shown on the right. This
has been written using Microsoft Visual Studio .net and the download files
contain the full workspace (solution) details to allow you to
immediately open and start editing or running this application. 
Even if you don't have Visual Studio, the source code is virtually self
explanatory with the most relevant sections being in "Form1.vb" which can
even be opened in a simple text editor such as notepad. The files are
zipped for convenience and may be downloaded by right clicking on the link
below and choosing "save target as" to begin the download.