Question regarding shielding

Hi all,

This is my first time playing with electronics. I had almost zero knowledge but during the last 3 months I understand quite a bit now. I was quite afraid of it (especially Linuxcnc, I was keeping Acorn ahead because of the ease) but I am quite enjoying it now. I have wired my lathe previously with a printer BOB and it ran successfully. Now I am getting it hooked with a mesa 7i96s card with nema 23 motors and a spindle encoder. Getting a mesa board here in India is quite hectic so I will ask some questions frequently so that I dont mess anything up. 

1. What are the 5V, GND pins on each stepper axis of the Mesa card used for?

2. I heard that you need shielded wires for steppers. So do I need to shield the pulse and direction wires from the mesa card to the drivers along with the wires from the drivers to the motor or just the latter is enough?

3. Even though I searched quite a bit about the enable signal of the drivers, I couldn't land on a decision on how to wire it. I understand that leaving it unconnected or having the pins low enables them and having them high disables them. I really dont want the steppers to be enabled all the time, maybe F1, F2 from Linuxcnc will disable-enable them. Any wiring suggestions?

4. There is a Frame GND on the Mesa card. Do I need to ground it?

Thanks in advance..


EDIT: I now understand what the 5v and GND is for on the mesa stepper axis segments. I somehow missed it on the manual..

Shielding can be a very deep topic but basically you can
1: Shield the wires (hopefully very short and not near high power/motor wires, can be challenging to debug/verify)
2: Use differential signals, routed together, ideally with a twisted pair

Differential is definitely the way to go, if your motor controller has separate D+/D- and S+/S- signals you should use them. Differential basically means one line will go high, the other will go low to represent a "1", and they will reverse to represent a "0". Doing it this way means that any electrical noise on the wires due to power supply noise, EMI, magnetic fields, etc. will affect both lines together.

Because differential signaling uses the voltage difference between the lines, most noise will not alter the signal.

For more info, lookup "Common mode noise" and "differential signaling".

If you do use differential signals, make sure to use either twisted pair (hacked Ethernet cables work well) or are routed very close together.

The frame ground on a 7I96/7I96S should connect to
the  earth ground. This is to protect the 7I96S from large
EMI/ static from the Ethernet connection. This is especially
important for noisy machines like plasma cutters.

The reason for the 5V and GND on the step/dir connectors
is to support single ended use. For single ended logic level
drives or drives with common cathode connected OPTOs,
you would typically use STEP+/DIR+ and GND. For drives
with common anode connected OPTOs, you would use
STEP-/DIR- and +5V