Receiving Invalid Data From Serial Port using SerialPort.ReadExisting()

Question

Recently we have connected one bluetooth device which receive data from our serial device. The bluetooth device further transmite this data to a Windows Mobile which is bluetooth enable. Baud rate of whole system is 19200 with 7 data bit and 1 stop bit.When we send command to serial device through bluetooth device it is accepting the command and respond accordingly. but some of data byte of string is desplay as question mark (?).

But in case we connect the serial device directly to PC, the string received is correct.

Code of vb.net program which I run in windows mobile is below:

Imports System
Imports System.IO.Ports
Imports System.Windows.Forms.TextBox

Public Class frmSelectComPort


Dim WithEvent port1 as serialport = _
New SerialPort(“Com2”,19200,Parity.Even, 7, StopBits.One)

 Private Sub MnuConnect_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MnuConnect.Click

    If port1.IsOpen Then
        port1.Close()
    End If
    port1.DtrEnable = True
    port1.RtsEnable = True
    port1.ReceivedBytesThreshold = 1
    port1.Open()

    Dim str1,strcmd,strReadSegment0 As String
    Str1="09RD000001"
    strchksum=23
    strcmd = New String(Chr(2) + str1 + Chr(3) + strchksum) + Chr(0)
    Delay(5000)
    port1.Write(strcmd, 0, strcmd.Length)
    System.Threading.Thread.Sleep(70)
    Delay(2000)
    strReadSegment0 = port1.ReadExisting
   ‘here I receive the following string "?09?D03?A D?

End Sub


Private Sub Delay(ByVal num As Double)
    Dim i As Double
    For i = 0 To num
    Next
End Sub

End Class

Command Given to Serial Port is " 09RD000001 23

Response given by Serial Port is "?09?D03?A D?

But I Expect the following input from serial port : " 09RD033A DA

Kindly provide the solution ASAP

Answer 1

Have you tried 8 databits, no parity, 1 stop bit? As long as both ends are set the same...

The ? can indicate that the encoding needs to be set.

Dim myEnc As Encoding = Encoding.GetEncoding("Windows-1252")
port1.encoding=myEnc