vb.net - receiving hex data over serial interface - vb.net

Question

I do have a device, which I communicate with over the serial Interface.
The communication is done in hex, so I send hex and I do receive hex.
Example: if I send "AA 00 03 89 18 0A 98 BB" the device reports back with "AA 00 02 00 80 82 BB".
My aim is to get a hand on the return value in an human readable way, respecively as a string.
The sending works fine, however the receiving is the part where I struggle hard and where I need help.
The sending part:
This is the part where I define the command to send:
Public Class ClassRfidWrapper
Public Function Command(ByVal theCommand As String) As Byte()
'Versuche.
Try
If theCommand = "SetBuzzer" Then
Dim bytes() As Byte = {&HAA, &H0, &H3, &H89, &H18, &HA, &H98, &HBB}
Return bytes
End If
Catch ex As Exception
Console.ForegroundColor = ConsoleColor.Red
Console.WriteLine("Class -> ClassRfidWrapper, Method -> SendCommand, Error -> " & ex.Message)
End Try
Return Nothing
End Function
End Class
This is the part where I send the hex message to the device:
Public Sub MySendSerialData(ByVal data As Byte())
'Versuche.
Try
If MyCheckIfSerialIsConnected() = True Then
'Mitteilung.
Main.MessageObject.MyMessage("message sent to device: ", Bytes_To_String2(data), 3)
'Log [LogWrapperToDevice]
Main.LogObject.MyLog(Bytes_To_String2(data), "LogWrapperToDevice")
SerialInterface.Write(data, 0, data.Length)
End If
Catch ex As Exception
Console.ForegroundColor = ConsoleColor.Red
Console.WriteLine("Class -> ClassSerialInterface, Method -> MySendSerialData, Error -> " & ex.Message)
End Try
End Sub
Do the sending:
SerialInterfaceObject.MySendSerialData(RfidWrapperObject.Command("SetBuzzer"))
Function to convert Hex to string:
Public Function Bytes_To_String2(ByVal bytes_Input As Byte()) As String
Dim strTemp As New StringBuilder(bytes_Input.Length * 2)
For Each b As Byte In bytes_Input
strTemp.Append(Conversion.Hex(b))
Next
Return strTemp.ToString()
End Function
The receiving part:
This is where I have the problems
Public Shared Sub DataReceivedHandler(sender As Object, e As SerialDataReceivedEventArgs)
Dim sp As SerialPort = CType(sender, SerialPort)
Dim data As String = sp.ReadExisting()
'Mitteilung.
Main.MessageObject.MyMessage("incoming serial data: ", CStr(data), 3)
'Log [LogDeviceToWrapper]
Main.LogObject.MyLog(CStr(data), "LogDeviceToWrapper")
End Sub
The problem is, I get garbage...
I understand, that .ReadExisting is the wrong way, as it interprets the received data as string, so I need an example code, of how to receive and convert the data to a byte array containing hex code, which I can subsequently convert to a string with my function Bytes_To_String2
Thanks for your help

Answer 1

Read the response buffer as a byte array.
Public Shared Sub DataReceivedHandler(sender As Object, e As SerialDataReceivedEventArgs)
Dim sp As SerialPort = CType(sender, SerialPort)
Dim respSize As Integer = sp.BytesToRead
Dim respBuffer As Byte() = New Byte(respSize - 1)
comport.Read(respBuffer, 0, respSize)
' Convert to string and additional processing ...
End Sub