Newbie (ageing rapidly!)

[Doddy]

MM: I don't have the NVUM, but do have the NVEM (the ethernet variant), and can say that they are largely okay, but come with issues, the first one being that they have a fixed pulse width of 2.25us output to the stepper drivers, from memory (and that ain't great) negatively switched but capable of sourcing or sinking current. The default installation in the manual suggested switching the positive input to the stepper driver and grounding the negative input - with my cheap stepper drivers that lead to the LED in the optocoupler being "On" significantly longer than "Off", coupled with the low performance optocouplers (4n25) and saturation on the phototransistor meant that the stepper drivers were missing steps (scoping input vs output showed a grim transfer function). So, word of warning on the NVUMs (assuming the motion controller is largely the same) - check that you're not in a position described above, changing the arrangement above can help (as can better stepper drivers or replacing optocouplers.... but you're a way from that yet by the sounds of things).

I've never tried USB on a CNC machine (only PPBoB and Ethernet). I did, however, once have a USB interface to a RepRap 3d printer. That was temperamental (occasional missed instructions which lead to offsets in the print space) and a shared view on the inter web pointed at the reliability of USB. Fortune smiled upon me and I managed to shear off the micro USB socket from the board by tripping over the cable - the easiest fix for me was tacking a bluetooth serial interface directly onto the Melzi board. Strangely, BT was infinitely more reliable than USB in that environment. I think USB and steppers and potentially disimilar grounds don't co-exist well.

The NVUM ??? plugin buttons - I have those with the NVEM. Not figured out which button does what but again, from memory, there's only a couple of very basic options to play with on the config screen, so long as those "stick" then the two buttons are likely OK and CANCEL - press one and check the config sticks. The ddream driver - sounds about right - and I think indicates this is likely a rip-off controller, but works to a fashion for me on a NVEM.

Open up the NVUM - you should find the inputs are Optocoupled already so external conditioning is not really needed. Just be aware that the ABS injection moulded case - the receptacle for the screws doesn't butt against the mating face on the other half of the case - so it's easy to overtighten and rip the plastic apart. Tighten to 0 white-knuckles loading.

What exactly doesn't work for you with the NVUM? I guess you've tried jogging with no joy?, I know with the NVEM driver on first start-up I can find (though never really bottomed it) that I can't jog until I home the machine. Maybe a driver issue, but I usually have a 2 minute tussle persuading the machine to start moving - either a G1 X1 feed through the MDI or a home resolves and I then get distracted and never investigate further.