MSComm DCD line change counter problem

[ikaracic]

Hello!
I am working on a little program that counts changes in the serial port CD line.
I have connected pin 4 (DTR) and pin 1 (DCD) to a button and I am trying to make a program that counts how many times button is pressed. Here is the code:

Private Sub Form_Load()
With MSComm1
    .CommPort = 1
    .Settings = "9600,n,8,1"
    .SThreshold = 1
    .RThreshold = 1
    .Handshaking = comXOnXoff
    .PortOpen = True
  End With
End Sub
Private Sub MSComm1_OnComm()
  Select Case MSComm1.CommEvent
Case comEvCD
     If MSComm1.CDHolding = True Then
Label1.Caption = Val(Label1.Caption) + 1
End If
End Select
End Sub

When button is pressed the label1 should show +1, but the problem is that the label1 sometimes show +2 or even +3 after button is pressed only once. I am very new to vb programing so I was wondering if someone could please tell me if this is possible, and if it is some code would be very helpful. Thank You in advance!

[dilettante]

Switch contacts bounce. Consider the information at http://all-electric.com/schematic/debounce.htm

[ikaracic]

Thank You Mate!!

That helped!
I just need a little bit more of Your knowledge. Can You please write me the code to do the same thing with ringing indicator (pin 9)? There is no RIHolding property.

Best regards

[ikaracic]

Does anybody knows? I found this site:
http://www.danielandrade.net/2005/11...inamp-control/

This guy used four buttons to control winamp. (dcd, dsr, cts and ri)
The first three have the holding property, but I don't know what to do with ringing indicator?
Some code would be very helpful. Thank You!

[ikaracic]

Anybody?

[DickGrier]

MSComm does not expose Ring Indicate state (because it was designed to work with a modem, where RI is transient, thus the only indication is via CommEvent = comRingEvent). The only way to read the RI state is via the UART Modem Status Register. You can download IOOcx from my homepage to do this. However, note, that this works only with built-in serial ports, where there is a physical UART.

If you are using a USB serial adapter, then there is no practical way to get the RI status, AFAIK. This "issue" is caused by the way that the serial port device drivers are written, and is historical in nature.

Dick (www.hardandsoftware.net)