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Posted 21 Jun 2004


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Oscilloscope control

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23 Jun 20042 min read
WTL Oscilloscope control.

Sample Image


This is a simple implementation of Oscilloscope control. This control shows last N points of user data. It has up to 8 channels (number of channels are defined by OSC_MAX_CHANNELS parameter in header file). Each channel can show only one curve (in this version). Oscilloscope includes zoom in implementation by X (Horizontal), by Y (Vertical), and by both axes simultaneously (Rectangle). Zoom out is also available by pressing right mouse button in channel area (hold CTRL key to full zoom out).

Using the code

To use this control in your application:

  • Design the dialog and add the Static control.
  • Add the Oscilloscope.h header file to your project.
  • Assign a OscilloscopeCtrl to your static control.
  • In OnInitDialog(), subclass OscilloscopeCtrl control to ID using the SubclassWindow method.

Don't forget to turn on any channels you need.

#include <span class="code-string">"Oscilloscope.h"</span>


class CMainDlg : public CDialogImpl<CMainDlg>
       MESSAGE_HANDLER(WM_INITDIALOG, OnInitDialog)          
    LRESULT OnInitDialog(UINT /*uMsg*/, WPARAM /*wParam*/, 
        LPARAM /*lParam*/, BOOL& /*bHandled*/);
    OscilloscopeCtrl m_oscill;     


LRESULT CMainDlg::OnInitDialog(UINT /*uMsg*/, WPARAM /*wParam*/, 
      LPARAM /*lParam*/, BOOL& /*bHandled*/) 
     m_oscill.SubclassWindow( ::GetDlgItem( IDC_AREA ) );     

After creating Oscilloscope control, you can set special colors for curves and background (for each channel), point styles (how to draw the data points of curves), turn on/off grid, padding, and set padding coefficient. Padding is auto calculating value and used to offset curve by Y axis. By increasing padding coefficient (k>1), it is possible to decrease the gap between curve and channel top boundary box. If k<1, the gap will be increased (then k != 0). You can change oscilloscope layout by turning on/off X and Y axes and changing their positions (up or bottom for X axis; left or right for Y axis). Important: X axis is only one for all channels and Y axis is unique for every channel.

m_oscil.UseGrid(true); // trun on grid
m_oscil.UsePadding(true); // use padding
m_oscil.PaddingCoef(2.0); // set padding coefficient
m_oscil.PointStyle(UTriangle); // set point style to UTriangle
m_oscil.GetChannel(0)->SetLnColor( RGB(0,255,0) ); // green curve
m_oscil.GetChannel(0)->SetBgColor( RGB(0,0,0) ); // white background
m_oscil.BottomXAxis(true); // adds bottom X axis
m_oscil.LeftYAxis(true); // adds left Y axis

Then you need to supply data for oscilloscope (pointers to double arrays). It's important that double arrays you pass to oscilloscope have to be global. To increase drawing speed, oscilloscope doesn't copy data to its buffers (!!!). The double arrays contains only Y values, oscilloscope calculates X values automatically by using user time.

// number of arrays have to be equal to OSC_MAX_CHANNELS !!!
// but if you don't need data for example
// for channel 1 the m_values[1] can be NULL
double*  m_values[OSC_MAX_CHANNELS];
size_t   m_cnt;
size_t   m_time;
m_oscil.SetPoints(m_time, m_values, m_cnt);


  • Removed using namespace std from header file :)
  • Added double buffering to avoid flickering on draw (thanks to Michal Mecinski)

      Demo program

      The small demo program shows how to use the oscilloscope control. Add buttons to control its layout, to change zoom mode, points styles, last points, and etc. You can change source code for any future usage.

    • License

      This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

      A list of licenses authors might use can be found here


      About the Author

      Web Developer
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      Comments and Discussions

      GeneralSpeed Pin
      Manohar B. Srikanth2-Aug-04 22:18
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      GeneralOsc screen Pin
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      Questionmissing files ? Pin
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      AnswerRe: missing files ? Pin
      autodebug15-Sep-04 14:57
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      GeneralImpressive Pin
      Michal Mecinski22-Jun-04 1:38
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