Hardware required for Lathe Macros

I'm trying to determine both minimum and nice to have hardware requirements when using the lathe macros.
Assume I already have the following:

• Suitable PC with touchscreen
• MESA 7i96s
• Stepper/Servo for both Z and X axis
• Encoder linked to spindle with A,B,Z outputs
• Manual Start/Stop & Fwd/Rev switches
• Pot presently controlling spindle speed.
• Scales on X & Z not sure the lathe macros need the actual position data but I definitely want the actual position displayed because my leadscrews have a lot of backlash. My assumption at this point is that I will (hopefully) be able to use the macros in a way that actual cutting occurs in one direction only and then the tool retracts, re-positions (including required backlash) and then continues on the next cutting pass, does that sound like a reasonable expectation?

The unclear to me at this point hardware:

1. Pretty sure I need a cycle start button, not sure about a cycle stop?
2. Do the lathe macros need Linux control of the spindle speed, or can I control that manually via the existing potentiometer?
3. Are limit switches required?
4. I will make a control panel so any nice to have features would be good to know about now so I can included them, perhaps a couple of  rotary encoders? what else would be good to have?

Much appreciated
 

There is no particular hardware requirement for Lathe Macros as it runs standard Gcode files with parameters.
1. I usually have a button for start, stop and pause but you can set your cycle start button up so it starts a program if it is stopped or stops it if it is running.
2. Not necessarily. If you want to use feed/rev (G95) you need software control of the spindle speed but you also need spindle feedback (ie an encoder) for that.
3. Not necessarily, you could just run on soft limits, although depending on the size of the motors and the robustness of your hardware they might be a very cheap way of avoiding expensive mishaps.
4. Depends on you personal preference really. Maybe have a look at some commercial panels for ideas. Most basic decision to make is whether you trust screen buttons to control machine motion (eg cycle start/stop, jogging, spindle on/off)

Note: you will need spindle feedback (ie encoder A/B and index) for threading.