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 0da5000200000000000000004315 

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chkSum = 0
For index = 1 To alRecBuf.Count() - 3
  chkSum += alRecBuf.Item(index)
Next
chkSum = chkSum Mod &HFF
If chkSum And &HFF Then
  chkSum = chkSum Xor &HFF
End If

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'===========================================================================================================================
    ' Receives an Hex string and returns a char with the checksum
    '===========================================================================================================================
    Public Function PowermaxChecksum(ByVal MyHexString As Object)

        Dim HexS() As String
        Dim aSrtring As String
        Dim Checksum As UShort = 0
        Dim HighByte As Byte
        Dim LowByte As Byte
        Dim I As Integer
        Dim bytes As Byte()

        ' Sample Message
        ' 0D AB 0A 00 01 00 00 00 00 00 00 00 43 06 0A      
        '  |                                      |  |
        '  |                                      |  Postample
        '  |                                      Checksum
        '  Preamble

        HexS = MyHexString.Split(" ")
        Dim data(HexS.Length) As Byte
        ' 1. Sum all the payload bytes in a word;.
        For I = 0 To HexS.Length - 1
            data(I) = CLng("&h" & HexS(I))
            Checksum = Checksum + CLng("&h" & HexS(I))
        Next

        ' 2. Subtract both high and low byte from FFFF; (ej FFFF-00-FF = FF00)
        bytes = BitConverter.GetBytes(Checksum)
        LowByte = bytes(0)
        HighByte = bytes(1)
        Checksum = &HFFFF - HighByte - LowByte

        ' 3. Low byte contains the checksum.
        bytes = BitConverter.GetBytes(Checksum)
        LowByte = bytes(0)
        Checksum = LowByte

        aSrtring = Conversion.Hex(Checksum)
        If aSrtring.Length = 1 Then
            aSrtring = "0" & aSrtring
        End If

        Return aSrtring
    End Function