I am using VS2005 and VB and the .Net 2 Serial Port class at 9600 8 N 1

I have been using some example code to connect to another device over a
serial port and issue text commands and receive feedback


Everthing works - but the characters sent are  getting mangled/dropped and
commands are not being completely read by the device;

eg sending "Get Serial"  is echoed as Ge  - Invalid Command"  The exact
amount of the original command echoed varies randomly. and the response
part - "Invalid Command" is always complete so it is just a sending problem.

All this  works just fine every time using Hyperterminal at 9600 8N1
In HT  if I send "Get Serial"  -  it returns " Serial = 123456" and this
always works!


The Serial Port class has lots of "knobs" to tweak various attributes such a
buffer size and timeouts
How should I set it up to emulate Hyperterminal which works perfectly?


Thanks

Bill

Hi,

I don't think there is anything to "tweek."  You didn't post any code, so
guessing is probably not profitable.  You can download a working set example
code from my homepage.  Perhaps it will get you started.  If you need more
help, post EXACTLY the code that you are implementing and I or someone else
may be able to help.

Dick

Here is the code.
I assumed - perhaps incorrectly that if I can send a receive characters then
the code is working and the issue is in the serial comm itself.

Bill
Public Class Form1

Dim WithEvents serialPort As New IO.Ports.SerialPort



Private Sub Form1_Load(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles MyBase.Load

For i As Integer = 0 To My.Computer.Ports.SerialPortNames.Count - 1

cbbComPorts.Items.Add(My.Computer.Ports.SerialPortNames(i))

Next

btndisconnect.Enabled = False

End Sub

Private Sub btnConnect_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles btnconnect.Click

If serialPort.IsOpen Then

serialPort.Close()

End If

Try

With serialPort

..PortName = cbbComPorts.Text

..BaudRate = 9600

..Parity = IO.Ports.Parity.None

..DataBits = 8

..StopBits = IO.Ports.StopBits.One

..Handshake = IO.Ports.Handshake.RequestToSendXOnXOff

..WriteTimeout = 1000

..ReadTimeout = 1000

..RtsEnable = True

..ReceivedBytesThreshold = 16

..NewLine = vbLf



End With

serialPort.Open()

lblmessage.Text = cbbComPorts.Text & " connected."

btnconnect.Enabled = False

btndisconnect.Enabled = True

Catch ex As Exception

MsgBox(ex.ToString)

End Try

End Sub

Private Sub btnDisconnect_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles btndisconnect.Click

Try

serialPort.Close()

lblmessage.Text = serialPort.PortName & " disconnected."

btnconnect.Enabled = True

btndisconnect.Enabled = False

Catch ex As Exception

MsgBox(ex.ToString)

End Try

End Sub



Private Sub btnSend_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles btnsend.Click

Try

serialPort.WriteLine("Get_Serial")

With txtdatareceived

..SelectionColor = Color.Black

..AppendText(txtdatatosend.Text & vbCrLf)

..ScrollToCaret()

End With

txtdatatosend.Text = String.Empty

Catch ex As Exception

MsgBox(ex.ToString)

End Try

End Sub



'-------------------------------------------

' Event handler for the DataReceived

'-------------------------------------------

'The delegate and the updateTextBox() subroutine is defined as follows:

'------------------------------------------------------

' 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(serialPort.ReadExisting)

..ScrollToCaret()

End With

End Sub



Private Sub serialPort_DataReceived(ByVal sender As Object, ByVal e As
System.IO.Ports.SerialDataReceivedEventArgs) _

Handles serialPort.DataReceived

txtdatareceived.Invoke(New myDelegate(AddressOf updateTextBox), New Object()
{})

End Sub

End Class


Show quoteHide quote

I just tried Dick's code and it works - Thanks!

So starting with working code I was able to find my problem - but not a
solution.

If I add a button to Dick's sample that writes my string then I see the same
error
With SerialPort

If .IsOpen = True Then

..Write("Get Serial" & vbCrLf)

End If

End With

So it seems that writing characters one at a time works  - but not strings.

Any ideas?


Show quoteHide quote

Hi,

There is no problem sending full strings that I know of (I do it all the
time).

However... Your device may expect a delay between each character (just as
though you had typed it).  So, sending the data one character at a time (use
a loop), and add a delay (say 50 mS) between each character).

This is a frequent problem when working with legacy hardware.  Back in the
"old days," assumptions were made that make our job a little harder at
times.

Dick

That fixed it!

Thanks

Bill


Show quoteHide quote

Great!

BTW, "Get Serial" & vbCr  should be all you need.  The Lf in your previous
code should be ignored by the connected device.  This makes it a little
simpler.

Dick

Framework and Window 2003
when CurrentPrincipal is set in async call back, NET 2.0 loses CurrentPrincipal
Two versions of .Net on the same server
Graph control
Mutually Exclusive C# Method