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  • Programming the Digi-Bee+ in Visual Basic

     Although Digi-Bee+ comes with it's own software (Logic-Lab Plus) 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.

    InitDgb( ) SetOutputs (outputs) and ReadInputs(inputs)

    InitDgb() is called somewhere near the start of your program and takes care of all of the USB comms initialisation and prepares the Digi-Bee+ for receiving messages.
    SetOutputs(outputs) can then be called at any time during your program to set the output pattern of on's and off's. The parameter outputs is simply a 16 bit integer values. In outputs bit0 corresponds to output 1, bit 1 to output2, etc.... In each case a logic value of 1 turns the output on and a value of 0 turns it off. For example the statement below would turn on the first three outputs...

    SetOutputs (7) since 7 in binary is 00000111

    and the following would turn on outputs 1, 2, and 4
    SetOutputs (11) since 11 in binary is 00001011

         To read the current state of the digital inputs simply pass an integer variable to the ReadInputs() function and use it’s value after the call. For example if inputs 2 and 4 are on, then the call…


    will result in the integer “inputval” containing the value 10.  This is 0000000000001010 in binary.

        To read the current values of the 4 analogue inputs pass 4 variables by reference to the ReadAnalogueInputs function….

    ReadAnalogueInputs(aip1, aip2, aip3, aip4)
    … which will result in the digitised amplitude of the 4 voltage levels on the 4 analogue inputs being returned in the supplied variables aip1 – 4. If , for example, the voltages on the 4 analogue inputs happen to be 1.0v, 2.0v, 2.5v and 3.75v respectively, then the above function call will result in the following values in the 4 variables…..
    aip1 aip2 aip3 aip4
    51,   102,  128,  196

    This assumes a “normal” sensitivity setting

    To set the sensitivity to other than 0-5v use the SetSensitivity function…
    SetSensitivity(1) sets high sensitivity based on current voltage reference
    SetSensitivity(0) sets normal sensitivity based on 0-5v

    In the above example if the following function call had been made prior to the ReadAnalogueInputs() function….
    Then the resulting values returned in a1 – a4 would be approximately double (subject to the maximum of 255). This assumes that the on-board voltage reference of 2.4v was used.

                                                     What could be simpler……………..

    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 three functions are made. The following is a program excerpt showing how this is done...

    Declare Function InitDgb Lib "dgb.dll" () As Boolean

    Declare Function SetOutputs Lib "dgb.dll" (ByVal outputs As Integer) As Boolean

    Declare Function ReadInputs Lib "dgb.dll" (ByRef inputs As Integer) As Boolean

    Declare Function ReadAnalogueInputs Lib "dgb.dll" (ByRef aip1 As Integer, ByRef aip2 As Integer, ByRef aip3 As Integer, ByRef aip4 As Integer, ) As Boolean

    Declare Function SetSensitivity Lib "dgb.dll" (ByVal HighNorm As Integer) As Boolean

        The first declaration states that the function InitDgb has no parameters, is found in dgb.dll and returns a boolean value. The second states that SetOutputs has one integer parameter passed by value rather than reference, is found in dgb.dll and also returns a boolean value. The third state that ReadInputs has one integer parameter passed by reference, is found in dgb.dll and, again, returns a boolean value.  The fourth passes 4 values by reference and the fifth by value etc....

    It should be noted that the
                                 Lib "dgb.dll"
                                                       lets the program know where to find the dgb.dll file. When written like this it assumes, since there is no path information, that the dgb.dll file can be found in the windows system directory ( c:\windows\system32 ) If you like you can copy the file dgb.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...

    Declare Function InitDgb Lib "c:\mylibrary\dgb.dll" () As Boolean



       To speed up your development of software for the Digi-Bee+ a complete working example is available for download below. It is called VBdigi and creates a very simple form based program that has individual buttons for various functions such as initialising the Digi-Bee+ 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.



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