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MSComm Control Example

Prerequisites
The MSComm32.ocx ActiveX control is licensed. Therefore, it must be legitimately installed onto the computer on which this script is run. Simply copying the control will not license it and the control will not work. The programmer has two options:

• Install Visual Basic 6.0 or Visual C++ 6.0. This will install a licensed version of the MSComm32.ocx ActiveX control onto the computer.
• Install the NETCommOCX ActiveX control from Richard Grier's web site. I have not personally tried it but I do have direct testimonial from another user who did not have the MSComm control installed on his computer and installed this control and used this example successfully. Mr. Grier's control is a wrapper around Microsoft's MSComm control. Grier uses an installation program to install the control on the computer, and this step likely register's the licensed control properly.

Introduction
This example is for those individuals who are interested in using script to do sophisticated serial comms on their computer. It shows four key concepts: receive, transmit, saving received data to a file, and formatting the received data with comma separators. Naturally, as a script, the program has no user interface, but is great for doing background processing, and it does not tie up the CPU. The example is setup to receive six characters and then store them into a file with comma separators between each pair of characters.
[/font] REM VBScript Example of using MSComm[/b] control for send and receive REM --------------------------------------------------------------------------- ' NOTES: ' This is a complete example of using the MSComm[/b] control distributed with Visual ' Studio 6 to both send and receive data. The received data is stored in a text ' file. Both binary and printable text characters can be received. The text file ' is stored in the same directory as this script. The number of characters to ' receive before ending the script is settable through 'MyThreshold'. ' For maximum efficiency of burst-mode data, the event handler buffers the ' incoming data before writing it to the file. Since it is not possible to ' know how many characters may be in the MSComm[/b] control's input buffer, the ' only sure way of knowing how many characters are received is to accumulate ' the count through a call to the control's InBufferCount property. While this ' may appear to be counter-intuitive, the control does not interrupt the program ' on every received character. It is not possible to know how many characters ' are waiting without using the InBufferCount property. When the Input() ' method is called, it will take InBufferCount number of bytes (all of them) out ' of the input buffer if the InputLen property is set to '0'. ' After the threshold number of bytes are received, the event handler processes ' the contents of the receive buffer by writing the contents to the log file ' two bytes at a time with commas separating each pair of bytes. Option Explicit Dim objTest ' MSComm[/b] control reference pointer Dim objFSO ' file system reference pointer Dim objLogFile ' file pointer Dim s ' general purpose string Dim path ' path to current directory Dim msg ' message sent out of comm port Dim flag ' indicates whether or not script continues Dim rxCnt Dim rxBuf Dim i const logfile = "\log.txt" ' file where received data is stored const MyPort = 1 ' COM1 const MyBaud = "57600" ' bps rate const MyThreshold = 6 ' how many characters to receive until done const comEvSend = 1 ' enumeration of comm events const comEvReceive = 2 const comEvCTS = 3 const comEvDSR = 4 const comEvCD = 5 const comEvRing = 6 const comEvEOF = 7 const comInputModeText = 0 ' enumeration of input mode constants const comInputModeBinary = 1 flag = 0 ' keep program running until comm event rxCnt = 0 Set objFSO = CreateObject _ ("Scripting.FileSystemObject") ' create a file system object path = objFSO.GetAbsolutePathName ("c:")' get the path to this directory Set objLogFile = objFSO.CreateTextFile _ (path & logfile, True) ' create a text file in local directory Set objTest = WScript.CreateObject _ ("MSCOMMLib.MSComm", "[/b]MSCommEvent_") ' second parameter (MSCommEvent_) + ' name of event (OnComm) creates the ' event handler that is called when ' the event fires objTest.CommPort = MyPort ' select a port to use objTest.InputLen = 0 ' if = 0, will retrieve all waiting chars objTest.InputMode = comInputModeText ' causes Input() to return string (not array) objTest.RThreshold = 2 ' must be non-zero to enable receive objTest.PortOpen = TRUE ' open COM port for use s = MyBaud & ",n,8,1" ' settings: baud,parity,bits,stop in BSTR objTest.Settings = s ' send to COM port msg = "Test Message " objTest.Output = msg ' send test message out of port While flag = FALSE ' put script in idle until comm event Wscript.Sleep (1000) Wend objLogFile.Close ' close log file objTest.PortOpen = FALSE ' close port Wscript.DisconnectObject objTest ' destroy object Wscript.DisconnectObject objFSO ' destroy object Wscript.DisconnectObject objLogFile ' destroy object Set objTest = Nothing ' uninitialize reference pointer Set objFSO = Nothing ' uninitialize reference pointer Set objLogFile = Nothing ' uninitialize reference pointer Wscript.Echo "Script completed." REM --------------------------------------------------------------------------- Sub MSCommEvent_OnComm ' OnComm event handler Select Case objTest.CommEvent Case comEvReceive rxCnt = rxCnt + objTest.InBufferCount rxBuf = rxBuf & objTest.Input If rxCnt >= MyThreshold Then For i = 2 To MyThreshold Step 2 objLogFile.Write (Mid (rxBuf, i - 1, 2)) objLogFile.Write (",") Next flag = TRUE rxCnt = 0 End If Case Else End Select End Sub