Clever idea from Jeremy S Cook to monitor a parallel port:

Parallel LEDinator  for DB25 Connector

I array of input/output LEDs for CNC DB25 parallel connector. Nice to have some extra blinkenlights, which is great to show what’s going on with your CNC, and could be applicable for any sort of DB25-based connection. Let me know in the comments if there’s any interest in these, and perhaps I’ll make them and/or the design available.

The KiCad design files are on GitHub.