Here’s a pretty nice parallel port oscilloscope –
This oscilloscope uses the SPP or EPP parallel port (LPT1) for reading the data from ADC. If your LPT1 is an ECP then the program automatically switches the LPT1 in byte mode (normal mode). BUT, not all parallel ports (LPT ports) are bidirectional. “Bidirectional” means, that except outputing data, the port can also read the data. How to determine if your LPT1 port is a bidirectional one? Start the LPTscope program and on the program menu select: “Bidirectional capabilities testing” then follow the given instructions.