Ah, the joys of trying to catch up on over 12 months of patching and upgrading servers, sadly between it and working through the finer details of our DR Plan there has been very little time for me to really invest much time in jscripts recently.

A few weeks ago I had an interesting conversation with a friend of mine. He asked me about whether or not it was possible to read values from a set of scales over a serial port through a jscript, they wanted a button that a user could push which would read the weight from scales and then submit it. I of-course replied confidently, yes – however you may need some fudging around to access the serial port – thinking in the order of using pinvoke.

As I was telling him about how when I last looked the .Net framework didn’t have direct functionality that supported interfacing to the COM ports, I searched msdn and came across a pleasant surprise, that pleasant surprise being System.IO.Ports and under that is a nice little object called SerialPort.

So, curious as I was I said I’d throw together a proof of concept.

As I didn’t have a set of scales to test, but I did have a Cisco switch handy I figured I’d just see what was involved in sending some data so it returned the initial command prompt. To be honest, the biggest hassle and nearly the most amount of time spent on this was moving the switch close enough to my computer and trying to find a power point!

Reading through the specifications that I was sent and some previous experience with retrieving data from serial devices that are dumb and just spew forth data, I decided that after each step I’d display a MessageBox. If you were looking at using this as a basis for your own solution you may want to look at saving things like the COM port settings, parity etc out to the registry or a configuration file rather than hard coding them as I did. Also there are some great examples of retrieving things like the available COM ports in the msdn documentation.

As mentioned, this is a proof of concept only, you can’t get much simpler than this but it should illustrate Opening/Closing and Reading/Writing from a serial port.

A few things to be wary of, when I was testing this I didn’t wrap any of the code in a try statement, when it crashed it took really nuked my Lawson Smart Office session. Getting an exception of the ReadLine is something I would expect to happen and potentially be a valid response due to a timeout. It would be prudent to also wrap the entire code in an exception handler.

Anyways, code commented as always.

import System;
import System.Windows;
import System.Windows.Controls;
import MForms;

import System.IO.Ports;

package MForms.JScript
{
    class SerialPortTest_000
    {
        public function Init(element: Object, args: Object, controller : Object, debug : Object)
        {
            // create our SerialPort Object
            // http://msdn.microsoft.com/en-us/library/system.io.ports.serialport.aspx
            var spSerialPort = new SerialPort();

            if(null != spSerialPort)
            {
                spSerialPort.PortName = "COM1";          // the COM port we are going to use
                spSerialPort.BaudRate = 9600;            // the Baud
                spSerialPort.Parity = Parity.None;       // parity - http://msdn.microsoft.com/en-us/library/system.io.ports.parity.aspx
                spSerialPort.DataBits = 8;               // databits
                spSerialPort.StopBits = 1;               // stopbits
                spSerialPort.Handshake = Handshake.None; // Handshake - http://msdn.microsoft.com/en-us/library/system.io.ports.handshake.aspx

                // timeouts
                spSerialPort.ReadTimeout = 500;
                spSerialPort.WriteTimeout = 500;

                MessageBox.Show("About to Open");
                spSerialPort.Open();                     // Open the serial port

                MessageBox.Show("About to Write");
                spSerialPort.WriteLine("\n");            // Cisco switches like a linefeed to be sent before they return anything

                MessageBox.Show("About to Read");

                // we will read two lines of data and display them
                // it is important that you wrap things in an exception
                // handler, if you don't when things go wrong they will
                // go *VERY* wrong and will typically take out Lawson
                // Smart Office
                // infact, the entire serial port sequence should be wrapped
                // in a try statement 
               try
                {
                    var strData : String = spSerialPort.ReadLine();

 
                    strData += spSerialPort.ReadLine();
                }
                catch(ex)
                {
                }
                

                // show the data
                MessageBox.Show("Data = '" + strData + "'");

                // close the serialport
                spSerialPort.Close();
            }

        }
    }
}

Have fun!