Hi Craig
I'm definitely ditching the xhc. Too many quirks. I don't understand the give and take between the motion controller and Mach4 output, but there seems to be something going on. The sound of the stepper motor varies in a pulsing fashion in exact time with the blinking communication light on the mc. I thought it was passive and just took orders, but it's becoming moot.
Right now I only have an arduino mega with grbl on it to play with as an alternative, and it is crisp and precise by comparison. Partly because Universal G code Sender does just that. It doesn't interpret the commands so what you ask for is what happens. It also prints the dialog on the command screen for every transaction, and the card reports back what it's doing. It's really very friendly by comparison, and I don't see right off what Mach4 can do that this thing can't. Except maybe edit the screens. It's freeware too. $40 for a Mega and you're rockin.
Are there any real advantages to running mach4 for a casual hobby mill?