China- BoB grounding questions; how to correctly power the board

from Best Wiring Practices Best Wiring Practices :

In most cases the common points of the heavy-duty power sections of the CNC system (eg, stepper motor or servo motor drivers, spindle motors etc) will be segregated from common points of the electrically-sensitive sections of the CNC (control interface boards, limit switches, tool probe circuitry etc) to prevent cross-contamination of the two systems.

If I understand correctly this means that we need three separated grounds in the system

1. PC input circuit consisting of LPT input and the USB. All on BOB
2. Driver logic circuit consisting of driver output part of BOB and input signal part of driver
3. Driver power circuit consisting of main PSU, driver power lines, coil lines

Currently I m a bit unsure whether enstops ase optically isolated as well which would mean the need a forth ground.

@pl7i92 reading your wiring chart I assume you might encounter the same problems I had since your grounds are all connected, right? The step down converters connect the PC side with the mains PSU as well, right?

OK, one more finding (which is really weired). In my setup there was no 5V input for the IO part connected. How can this work? As mentioned before, the machine worked pretty well!