Android Question Cannot write specific sequence of byte to serial port

Hi ,
I'm writing a code that use serial port comunication.
I' need to write a specific sequence byte to serial port to initialize the attached device.

in hex
28 02 AF E7 FF 00 C1
decimal
40 2 175 231 255 0 193

In classic VB I may use the followin code:

With MSComm1
End With
MSComm1.PortOpen = True
Dim Buffer As String

Buffer = Chr("&h28") & Chr("&h02") & Chr("&hAF") & Chr("&hE7") & Chr("&hFF") & Chr("&h00") & Chr("&hC1")
MSComm1.Output = Buffer


Using b4j or b4a I try using Astream object writing byte sequence
dim b() as byte
b(0) = 40
b(1) = 1
b(2) = 126
b(3) = 10
b(4) = 1
b(5) = 7
astream.Write( b)
works !!

b(0) = 40
b(1) = 1
b(2) = 234
b(3) = 228
b(4) = 1
b(5) = 7
astream.Write( b)
does not works !!!

I also try sendig word instead of byte with following code with no result !!

dim b(6) as string
Dim bc As ByteConverter
dim J as int

b(0) = "40"
b(1) = "2"
b(2) = "175"
b(3) = "231"
b(4) = "127"
b(5) = "0"
b(6) = "193"

For J = 0 To 6
Dim I As Short = data(J)
Dim bytes() As Byte = bc.ShortsToBytes(Array As Short(I))
Try
If astream.Write( bytes) Then
' ...
Else
' ...
End If
Catch
Log("error ...")
End Try
Next

Please help me.