Visual Basic Joystick Control

The 15 pin joystick gameport on a PC is a sophisticated anolog-digital converter capable of monitoring a variable resistance between 0 and 100,000 ohms.

Using this port and visual basic it is possible to create powerful, graphic applications to monitor temperature, light levels, motion, stress and any thing that can be monitored with a changing resistance.

To use your gameport with Visual Basic you must install a joystick control. There are many available on the internet as shareware or freeware.

Download the Mabry Joystick Control from: http://www.mabry.com/joystk/index.htm

If the above URL has changed, search the Mabry site for their Joystick control at: http://www.mabry.com

After downloading, run the self installing file. This will load the needed controls in Windows/system

Using the Joystick Control

1. Connect a joystick to your computer.
(Must be installed in Control Panel)

2. Start Visual Basic (5 or 6)

3. "right click" on the toolbox - select "components"

4. Select the "controls" tab.

5. Scroll to Mabry Joystk Control, tick the box.

6. A Joystick control should appear in the toolbox.

7. Add a Joystick control to the form. ("double click")

8. Add two text boxes to the form.

9. Double click on the Joystick control (open code window).

10. Select "move" in procedures/events box ("button down" and "button up" are the other options).

11. Enter these two lines of code to "read" the x and y axis of the joystick:

Text1.text = X
Text2.text = Y

12. Run

As you move the joystick, the numbers displayed in the text boxes will change with the motion.

Your computer is measuring and displaying the resistance created by your joystick. Replace your joystick with a thermistor and you are measuring temperature. Replace your joystick with a photo resistor (CdS cell) and you can create a security system or precision race timer.

Check out the Computer Engineering projects for information on making the connections.

This screen capture shows the display generated by VB code monitoring the two resitors connected to the gameport.

Download source code (VB 5) to create basic graph as above:

hila_port_chart.frm

hila_port_chart.vbp

Select "save to disk" when prompted.
Important: calibrate your joystick in "control panel".

The code:

Here is the code used to generate the above display
"grid" is a subroutine used to generate the grid.

The form requires three command buttons, two text boxes, Maybry joystick control and one picture box.

Dim c, n, X, Y As Integer

Private Sub Command1_Click()

Call grid ' calls subroutine that produces the grid
Joystk1.Enabled = True

End Sub

Private Sub Command2_Click()

Joystk1.Enabled = False

End Sub

Private Sub Command3_Click()

Joystk1.Enabled = True

End Sub

Private Sub Form_Load()

    Width = Screen.Width * 0.75 'sets form to 75% of screen
    Height = Screen.Height * 0.75
    Left = (Screen.Width - Width) / 2 ' centers form
    Top = (Screen.Height - Height) / 2

End Sub

Private Sub Joystk1_Move(ByVal X As Long, ByVal Y As Long, ByVal Z As Long)

Text1.Text = X
Text2.Text = Y

Picture1.PSet (c, X / 250), QBColor(1)
Picture1.PSet (c, Y / 250), QBColor(4)

c = c + 1

    If c > 600 Then Picture1.Cls
    If c > 600 Then Call grid 'calls procedure "grid" produces lines
    If c > 600 Then c = 0

End Sub

Public Sub grid()

    Y = 20
    For n = 1 To 9
    Picture1.Line (0, Y)-(600, Y), RGB(0, 255, 0)
    Y = Y + 20
    Next n

    Picture1.Line (0, 99)-(600, 99), RGB(200, 200, 200)
    Picture1.Line (0, 100)-(600, 100), RGB(200, 200, 200)
    Picture1.Line (0, 101)-(600, 101), RGB(200, 200, 200)

    X = 20
    For n = 1 To 29
    Picture1.Line (X, 0)-(X, 200), RGB(0, 255, 0)
    X = X + 20
    Next n

End Sub

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