SerialPort get less byte

[selimsl]

Hello everyone,

I am writing a program which communicates with a device(Energy Meter) via com port of my computer. I am using a RS232/RS485 converter. Because the device that I want to communicate with only supports RS485 communication media.
I have two different brand of converters
1) Moxa converter
2) Evir converter (a very cheap converter)

and I have two programs to communicate with Energy Meter
1)My program that I am writing in VB.NET
2)MBPoll (A program that I've downloaded from internet)

MBPoll can communicate with Energy meter if I use Moxa converter or Evir converter

But

My program can communicate with Energy meter if I use Moxa converter. If I use Evir converter it doesnt communicate. I get everytime less byte then expected. Do you have any Idea why I get less bytes when I use Evir converter. Evir converter is a cheap converter with low quality but MBPoll converter can communicate with it, so something should missing in my code .

Here is my code

     Private Sub DataReceivedEventHandler(ByVal sender As Object, ByVal e As IO.Ports.SerialDataReceivedEventArgs) Handles objSerialPort.DataReceived
        '**************************************

        Dim spTemp As SerialPort = CType(sender, SerialPort)
        Do While (spTemp.BytesToRead > 0)
            strInputBuffer &= spTemp.ReadExisting
        Loop


        '**************************************
        Dim strReturn As String
        strReturn = strInputBuffer
        '**************************************
        Dim strTemp As String = String.Empty
        For intTemp As Integer = 0 To strReturn.Length - 1
            strTemp &= Hex((Decoder(strReturn.Substring(intTemp, 1), 1252))).PadLeft(2, Chr(48))
        Next
        strReturn = strTemp
    End Sub

Thanksss in advance ...