I realize it has been a long time since this thread was active. I'm a new user of this plugin and after getting it working, i want to contribute back to all those posts and help as it may be of help to others.
1) I ordered a RS232-485 converter, a male/female dongle with small circuit board and 5 or 6 terminal clamps. Did not work. I wanted to go this way to use the onboard 232 and save a USB, so much for that.
2) Ordered the cheaper USB to 485. Wired it, no luck. Reveresed the wires, presto!
3) I had the same estop issue as a lot of people. Estop would not stop the spindle. What I did to fix it was actually use a Normally Open relay on a second bob, port 2, pin 14, set PD001 to 1 (PD002 to 2), the NO relay connected to FOR and DCM on the VFD, tell Mach3 to use spindle relay on that output port and tada! Mach3 starts/stops the spindle, can set the speed and on estop, stops the spindle (by opening the relay)! I know somewhere there is a warning to disable spindle relays, but for me it works, and works just how I want it.
thanks to all those who have posted both help and problems, the knowledge is great.
Cheers