If SerialPort1.ReceivedBytesThreshold = 33 Then ' 33 bytes received
                SerialPort1.Read(sadj, 0, 17)               'this is the ASCII block (as string)
                For bnum = 0 To 15
                    SerialPort1.Read(sdata, bnum, 0)        'read the data bytes one at a time
                Next bnum
                sadj(0) = " "
                label1.Text = sadj                          ' display the text string
                flags2 = sdata(15)                          ' define the flags byte
                If Not flags2 And &H4 Then                  ' do next if bit = 0
                    lhighbyte = sdata(0)
                    llowbyte = sdata(1)                     ' form into 16 bit word
                    lrpm = (lhighbyte * &H100) Or llowbyte  'hex to decimal conversion
                    Label2.Text = (CStr("RPM " & lrpm))     ' display the result

For bnum = 0 To 15
    SerialPort1.Read(sdata, bnum, 0)        
Next bnum

const UInt16    RX_BUFF_SIZE            = 4096;
        const UInt16    REQUEST_SIZE            = 800;


        public Form1()
        {
            InitializeComponent();

            serialPort1.BaudRate                = 115200;
            serialPort1.DataBits                = 8;
            serialPort1.StopBits                = System.IO.Ports.StopBits.One;
            serialPort1.Parity                  = System.IO.Ports.Parity.None;            
            serialPort1.ReadTimeout             = 100;
            serialPort1.WriteTimeout            = 100;
            serialPort1.ReadBufferSize          = RX_BUFF_SIZE;
            serialPort1.ReceivedBytesThreshold  = REQUEST_SIZE;
            serialPort1.Handshake               = System.IO.Ports.Handshake.None;
            //serialPort1.Encoding                = System.Text.Encoding.GetEncoding(28591);
            //serialPort1.Encoding                = System.Text.Encoding.GetEncoding(1252);
            //serialPort1.Encoding                = System.Text.Encoding.GetEncoding("Windows-1252");
            serialPort1.DiscardNull             = false;
            serialPort1.DtrEnable               = false;
            serialPort1.RtsEnable               = false;
            //serialPort1.BaseStream.ReadTimeout = 10;  //???  

       }

        // === DUMP button click EVENT ===//
        private void button1_Click(object sender, EventArgs e)
        {
            serialPort1.Close();
            serialPort1.PortName = comboBox1.Text;
            
            //try to open
            try
            {                
                serialPort1.Open();
            }
            catch (Exception exp)
            {
                MessageBox.Show(exp.Message);
                return;
            }

            Load_Timers();
            Load_Retry();

            //SEND START COMMAND : set Address & Size
            Mem_Adr = 0;    Mem_Size_Req = REQUEST_SIZE;
            send_cmd_on_serial_port(Mem_Adr, Mem_Size_Req);

            // manage controls to receive
            Flag_Start = true;
        }

        //============ SERIAL PORT DATA RECEIVE FUNCTION ============//
        private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
        {            
            if (Flag_Start == true)
            {
                if (manage_new_packet() == true)
                    {
                    // ===> OK <=== //

                    Load_Timers();          //re load
                    Load_Retry();           //re load

                    Log_packets++;

                    if (Flag_End == false)
                        {
                        Mem_Size_Req = REQUEST_SIZE;
                        send_cmd_on_serial_port(Mem_Adr, Mem_Size_Req);
                        }
                    }   //if NOK, wait timer expiration for retry                  
            }
        }


        private bool manage_new_packet()
        {
            UInt16 len_data, len_for_crc;
            SERIAL_CMD cmd;
            UInt16 crc;
            UInt16 i;
            
            //check serial port status
            if (serialPort1.IsOpen == false)
            {
                Clear_RX(true);
                return(false);
            }

            //Read serial port bytes
            while (serialPort1.BytesToRead != 0)
            {
                RX_buff[idx_rx] = (byte)serialPort1.ReadByte();
                idx_rx++;

                if (idx_rx >= RX_BUFF_SIZE)         //protection
                {
                    Clear_RX(true);
                    Log_errors = "buffer overflow";
                    return (false);
                }
            }

            //Check packet parameters
            
            [...buffer analisys...]

            Clear_RX();
}

        //============ SERIAL PORT DATA "CLEAR RX PARAMETERS" ============//
        private void Clear_RX(bool dummy)
        {
            UInt16 i;

            serialPort1.DiscardInBuffer();  //free the buffer from data...

            for (i = 0; i < RX_BUFF_SIZE; i++)
                RX_buff[i] = 0;
            
            idx_rx = 0;                        //clear Rx index
        }

            serialPort1.BaudRate                = 115200;
            serialPort1.DataBits                = 8;
            serialPort1.StopBits                = System.IO.Ports.StopBits.One;
            serialPort1.Parity                  = System.IO.Ports.Parity.None;            
            serialPort1.ReadTimeout             = 10;
            serialPort1.WriteTimeout            = 10;
            serialPort1.ReadBufferSize          = RX_BUFF_SIZE;
            serialPort1.ReceivedBytesThreshold  = 8;
            serialPort1.Handshake               = System.IO.Ports.Handshake.None;
            //serialPort1.Encoding                = System.Text.Encoding.GetEncoding(28591);
            //serialPort1.Encoding                = System.Text.Encoding.GetEncoding(1252);
            //serialPort1.Encoding                = System.Text.Encoding.GetEncoding("Windows-1252");
            serialPort1.DiscardNull             = false;
            serialPort1.DtrEnable               = false;
            serialPort1.RtsEnable               = false;


        //============ SERIAL PORT DATA "MANAGE PACKET RECEIVED" ============//

        public bool manage_new_packet()
        {
            UInt16 len_data, len_for_crc;
            SERIAL_CMD cmd;
            UInt16 crc;
            UInt16 i;
            
            //check serial port status
            if (serialPort1.IsOpen == false)
            {
                Clear_RX();
                return(false);
            }

            //check message
            if (serialPort1.BytesToRead >= 1)
            {
                RX_buff[0] = (byte)serialPort1.ReadByte();
                idx_rx++;
                cmd = (SERIAL_CMD)RX_buff[0];
                if (cmd != SERIAL_CMD.SERIAL_DUMP_REPLY_TO_PC)
                {
                    Clear_RX();
                    return (false);
                }
            }
            else
                return (false);

            if (serialPort1.BytesToRead < REQUEST_SIZE)
            {
                int Timer_tmp = System.Environment.TickCount;
                do
                {
                    //wait...
                } while (Timer_tmp + 100 > System.Environment.TickCount);

                if (serialPort1.BytesToRead < REQUEST_SIZE)
                {
                    Clear_RX();
                    return (false);
                }
            }

            //Read serial port bytes
            while (serialPort1.BytesToRead != 0)
            {
                RX_buff[idx_rx] = (byte)serialPort1.ReadByte();
                idx_rx++;

                if (idx_rx >= RX_BUFF_SIZE)         //protection
                {
                    Clear_RX();
                    Log_errors = "buffer overflow";
                    return (false);
                }
            }

            //process result
            ....
            ....

        //============ SERIAL PORT DATA RECEIVE ERROR ============//        
        private void serialPort1_ErrorReceived(object sender, System.IO.Ports.SerialErrorReceivedEventArgs e)
        {
            int dummy;

            Log_errors = "Serial Error";
            while (serialPort1.BytesToRead != 0)
                dummy = serialPort1.ReadByte();
        }