In Visual Basic in a PC Windows environment the program you write does not directly control the PC comm port Tx and Tx lines. These are controlled via some 16450/16550 UART compatible hardware burried someplace in your PC. Windows has an operating system API that is used by applications to control the COM ports. In Visual Basic you have your software interface via a control called MSCOMM. This is a layer of software (in a DLL I seem to recall) that adapts the Windows API interface to the Visual Basic programming environment. In order to send and receive serial data out of and into a PC using Visual Basic you need to learn how to use this MSCOMM control. There is an excellent book on this subject that can help you out tremendously.

Look at web site www.mabry.com for a book called Visual Basic Programmers Guide to Serial Communications by Richard Grier. ISBN 1-890422-25-8. It is best to purchase this direct from the WEB site to ensure you get the latest version of the book which is presently in its 3rd edition. I have the Second Edition - Date of Printing: August 31, 2001.

After this book you will be a PRO on serial ports with Windows and Visual Basic on the PC. I know when I tackled a VB project a couple of years ago I was kind of on the dark about MSCOMM. This book clearly answered EVERY question I had and is chock full of sample code.

Michael Karas