http://www.blogigo.com/naeimabadi en CSharp CSharp Mon, 07 Apr 2008 09:53:00 +0200 daily 1 i, if you use the input as string then you will send two chars which are "1" followed by a "2". if you want to send the value 12 then you will have to do the following:   private void send_data() { byte[] buffer_2_send = new byte[1]; byte data_2_send = 0;   data_2_send = Byte.Parse(textBox1.Text);//this way you will get the value 12 in your variable   //we will use a buffer because the serial_port.Write takes either a string or a buffer of data buffer_2_send [0] = data_2_send ;   serial_port.Open(); serial_prort.Write(buffer_2_send, 0, buffer_2_send.Length);//write data on the serial port serial_port.Close(); }     Mon, 07 Apr 2008 09:53:00 +0200 http://www.blogigo.com/naeimabadi/serial-communication-a/2/ http://www.blogigo.com/naeimabadi/serial-communication-a/2/ this is about serial comm  Mon, 07 Apr 2008 09:42:21 +0200 http://www.blogigo.com/naeimabadi/serial/1/ http://www.blogigo.com/naeimabadi/serial/1/