Yippeeee!

Finally I have electrons going in and out of the right places on the NVUM motion controller.
It was the plugin. The supplier kept assuring me they had provided the correct one. Big surprise, they hadn't. Got hold of the v2.1 plugin and it leapt into life. I've offered to tell them how to get it working if they settle my invoice for about 5 hours of my time!

The bit of signal conditioning I referred to earlier is simply due to the highZ inputs. The opto inputs only sink about 1.8mA and switch on at around 2v, that could be a problem from noise pickup. So a 680R pullup and 100nF capacitor to GND plus a 3v zener to raise their transition voltage should make them much more immune to spurious signals. As observed before there are no isolation or common mode problems with opto inputs.

Now just need to connect it to the rest of the gubbins....... (and find out if USB is as flaky as suggested).

MANY MANY Thanks for all the help and suggestions.