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06.12.2008 at 11:20AM PDT, ID: 23480562
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9.0

Reading asynchronous serial port data in VB 2005

Asked by hsano6294 in Microsoft Visual Basic.Net, Visual Studio

Tags: ,

Hello everyone,

I'm developing a driver that sends out text commands via serial port to an instrument. When that instrument is finished executing the command, or an error results, it will send back a text result. I expect this message will be less than 15 characters long.

1) I'm able to send out the commands and have the instrument respond, but am having difficulty capturing the Event and the message, as I'm new to Serial Communication and Event Handling. I've attached the code I've written.

2) What is the best way to wait for a response, with a given timeout value? Each command should be followed by a response, successful or not.

3) Is it better to open the COM port once or open and close it before/after each command?

Thanks!
Haj

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Module Module1
 
    Sub Main()
        Dim strCommand As String
        Dim CtrlJ As New Char
        Dim strReset As String ' Reset command
        Dim strPlateRequest As String ' Plate request command
        Dim strPlateReturn As String ' Plate return command
        Dim strReturnValue As String ' Post-command status returned from Q-Stack
 
        ' Commands have a <LF> (Ctrl-J or ASCII (10)) before and after.
        CtrlJ = Chr(10) ' Ctrl-J = Linefeed (ASCII)
        strReset = CtrlJ & "AK5=1" & CtrlJ
        strPlateRequest = CtrlJ & "AK3=1" & CtrlJ
        strPlateReturn = CtrlJ & "AK4=1" & CtrlJ
 
        strCommand = strReset ' Subsitute any of the commands for testing purposes
        OutToCOM4(strCommand, False)
 
        strReturnValue = ""
        InFromCOM4(strReturnValue) ' Wait for status from instrument before proceeding
        MsgBox(strReturnValue)
 
    End Sub
 
    Public Sub OutToCOM4(ByVal serialData As String, _
        ByVal useLineTermination As Boolean)
        Dim com4Port As IO.Ports.SerialPort = Nothing
 
        Try
            ' ---- Access the port.
            com4Port = My.Computer.Ports.OpenSerialPort("COM4", 9600, IO.Ports.Parity.None, 8, IO.Ports.StopBits.One)
            ' COM Port, baud rate, parity, data bits, stop bits
 
            ' ---- Write the data.
            If (useLineTermination = True) Then
                com4Port.WriteLine(serialData)
            Else
                com4Port.Write(serialData)
            End If
 
            ' ---- Finished with the port.
            com4Port.Close()
 
        Catch ex As Exception
            MsgBox("Error writing data to serial port: " & _
                ex.Message)
 
        Finally
            If (com4Port IsNot Nothing) Then com4Port.Dispose()
            com4Port = Nothing
 
        End Try
    End Sub
 
    Public Sub InFromCOM4(ByVal returnData As String)
        Dim com4Port As IO.Ports.SerialPort = Nothing
 
 
        Try
            ' ---- Access the port.
            com4Port = My.Computer.Ports.OpenSerialPort("COM4", 9600, IO.Ports.Parity.None, 8, IO.Ports.StopBits.One)
            ' COM Port, baud rate, parity, data bits, stop bits
 
            ' ---- Wait for incoming data.
            '--->>>   What is the best way to wait for incoming data? <<<---
 
            ' ---- Read the data.
            '--->>>   returnData = com4Port.??? ' How do I capture the incoming data? <<<---
 
            ' ---- Finished with the port.
            com4Port.Close()
 
        Catch ex As Exception
            MsgBox("Error reading data from serial port: " & _
                ex.Message)
 
        Finally
            If (com4Port IsNot Nothing) Then com4Port.Dispose()
            com4Port = Nothing
 
        End Try
    End Sub
 
End Module
[+][-]06.13.2008 at 12:49AM PDT, ID: 21776720

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About this solution

Zones: Microsoft Visual Basic.Net, Visual Studio
Tags: Micros, VisualBasic 2005
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Solution Provided By: AkisC
Participating Experts: 1
Solution Grade: A
 
 
[+][-]07.22.2008 at 04:13AM PDT, ID: 22058002

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