Using LPT port as logical scanner and tester

Sometime you need to connect some device to computer and check how it works. It is possible to use printer port for digital scanner and logical analyzer. If using standard print port (SPP) there is 8 output lines and 5 input lines. If using enhanced printer ports all data lines are multidirectional. You can read and write to them. In old operating systems it was very easy to program port. Just access &H378-&H37F port (for LPT2 278-27F) in any program and you can read information. But after invention of protected memory, direct communication with hardware is impossible. So if you have Windows 2K or Windows XP you must use special drivers to do simple jobs. I needed to change some values and has written small program in MS VB. To run it you must have Microsoft visual basic runtime.

Port tool is very simple software. Start it and look to the picture:

Just press on left column to change value on data pins (pin2…pin9) and read data from control pins. By default, program reads from LPT1. To use any other port, just enter new value is fields below. The program is not foolproof- you can enter any value and change any port. So, be careful.