How to Code for RS232 in Visual Basic? Part 3 – Example

You can download the example program written in Visual Basic 6.0 from the following link:

MsCommSample.zip

Sample includes detailed explanations as comment lines, so I am not going to explaing details of coding in this post.

To test the software you need to have a null modem cable if you want to communicate two computers.

You can make your own cable by soldering pins of two female DB9 connectors as follows.

Connector 1                   Connector 2
Pin 2 <---------------------> Pin 3
Pin 3 <---------------------> Pin 2
Pin 5 <---------------------> Pin 5

If you just want to test how data is sent and received on your computer, you just need one connector; short circuit pin 2 and pin 3:

Connector 1
Pin 2 <--
        |
Pin 3 <--

Make the cables at your own risk, short circuiting any pins other than 2 and 3 may damage serial port of your computer.

By default, software opens the Com1 port in 9600 bauds, no parity, 8 data bits and one stop bit without handshaking protocol. You can change it in source codes.

You also need to have Visual Basic 6.0 software to edit, debug and recompile program.