Comments by mtopaltr (Top 1 by date)

Martinus, just to let you inform about the solution. The code below here helped me. FYI

private static void SendCommand(byte[] buffer)
{
Thread.Sleep(10);
serialPort1.Parity = Parity.Mark;
serialPort1.Write(buffer, 0, 1);
Thread.Sleep(10);
serialPort1.Parity = Parity.Space;
serialPort1.Write(buffer, 1, buffer.Length - 1);
}