ScopePar is a freeware and turns a PC into a multi-channel oscilloscope module utilizing the parallel port, the user interface to which is SeriCon on other PC. If you have an old PC, boot it by dos to run ScopePar and control it by SeriCon on your GUI PC through serial port. The free trial version of SeriCon is enough in usual cases. Important features are:

• ScopePar is now a 5 channel square wave oscilloscope. Square waves mean that it just reads the high or low levels of the port pins (Later versions may be able to show curves, requiring ADC attached to the port). SeriCon shows only 2 channels, unless you have the full license.

• Sampling rates around several 100kHz can be reached.

• The measurement can be triggered by the first channel. You can select the level change (low-to-high or high-to-low).

• The system to measure also can be triggered by the output data pins just before a measuremet period starts.

• The measurement can be automated by specifying the period of sending the command from SeriCon (with the full license)