Au123

 I have a program that sends and receives data from pc to OMRON E5EK digital controller (I am using VB .NET), and I have a problem in receiving data from the controller. I suppose that I wrote the correct command, and yet it gives '??' response, when the correct one should give @ character at the beginning of the response and end with CR (Carriage Return).  Here is my program: Public Class Form1     Dim TX, RXD, FCS As String     Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load         MSComm1.Settings = "9600,E,7,2"         MSComm1.CommPort = 4         MSComm1.PortOpen = True     End Sub     Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick         TX = "@001000000"         Call GetFCS()         txtRequest.Text = TX + FCS + "*"         Call communicate()         txtResponse.Text = RXD     End Sub     Private Sub GetFCS()         Dim L As Integer         Dim A As String         Dim TJ As String         L = Len(TX)         A = 0         For J = 1 To L             TJ = Mid(TX, J, 1)             A = Asc(TJ) Xor A         Next J         FCS = Hex(A)         If Len(FCS) = 1 Then FCS = "0" + FCS     End Sub     Private Sub communicate()         Try             RXD = ""             MSComm1.Output = TX             RXD = MSComm1.Input         Catch ex As Exception             RXD = "Communication Error"         End Try     End Sub End Class   Can anybody help me to fix this problem? Thank you!