Serialport.Readexisting strange behavior

[learning]

I'm using the following to read a serial port. When run it displays the data correctly but stepping through the program I find that it loops through the serialdatarecieved event for each character of the port input rather than reading all of it. So _msg only equals one letter at a time. I'm trying to set a variable equal to the entire input stream but only get one character of it.

The end goal is to capture all of the data available on the port when the event triggers so that this data can then be processed. I tried using the bytestoread function, which gets the correct number of bytes to read, and then looped through to read a byte at a time but that didn't seem to work as I expected either. It just kept reading the first byte.

Any help you can offer would be appreciated.

Thanks

Imports System.IO.Ports
Public Class CommTest
    Dim WithEvents SerialPort As New SerialPort
    Dim _msg As String
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If SerialPort.IsOpen Then
            SerialPort.Close()
        End If

        Try
            With SerialPort
                .PortName = "COM1"
                .BaudRate = 9600
                .Parity = IO.Ports.Parity.None
                .DataBits = 8
                .StopBits = IO.Ports.StopBits.One
            End With
            SerialPort.Open()

            lblMessage.Text = "COM1 Connected."
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub
    Private Sub DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort.DataReceived
        _msg = SerialPort.ReadExisting
        txtDataReceived.Invoke(New myDelegate(AddressOf updateTextBox))
    End Sub

    '------------------------------------------------------
    ' Delegate and subroutine to update the Textbox control
    '------------------------------------------------------
    Public Delegate Sub myDelegate()
    Public Sub updateTextBox()
        With txtDataReceived
            .Font = New Font("Garamond", 12.0!, FontStyle.Bold)
            .SelectionColor = Color.Red
            .AppendText(_msg & vbCrLf)
            .ScrollToCaret()
        End With
    End Sub

  
End Class

 

[learning]

I've found a way around this by reading individual bytes and converting them to characters but would still like to know what was going on with the original code if anyone has an idea.

Thanks.

 

[tozzun]

I've found a way around this by reading individual bytes and converting them to characters but would still like to know what was going on with the original code if anyone has an idea.

Thanks.

you need to change ReceivedBytesThreshold property. Default it is set to 1 so whenever 1 char is recieved your method will be calling.

 

[learning]

Boy, you had to dig deep to find this thread. I posted it a year ago. I do appreciate the answer though and had found that some time ago. Should have posted it here, however, I won't necessarily know the length to read. It does answer my original question and I appreciate your responding.

Thanks.