The following test writes to the serial port and reads from the same port.

(Select Start>>Programs>>Accessories>>Hyperterminal.

1. Double-click on the Hypertrm icon.
2. If you are asked if you would like to install a modem, select No.
3. You are prompted to select an icon to represent the connection you are about to define. Choose any one, and name the session.
4. In the next Pop-Up menu, choose direct to COMx where x is the number of the COM Port you are testing.
5. Set the flow control setting to None. You may leave the other settings in the next dialog box, though you can increase the speed if you like.
6. Select File » Properties from the menu bar, select the Settings tab, and then push the ASCII Setup button.
7. Check the option for Echo typed characters locally.
8. Start typing. If you see double characters (that is, you see two characters for every one you type), the serial port is setup correctly and is functional.