Mesa spindle encoder - do I need it?

Dear all,

I'm in the process of converting a lathe to CNC. As I would still like to maintain the ability to use it "by hand" I'm considering replacing the hand wheels by encoders and adding glass-scales. The glass-scales are ideally also processed by linuxcnc to have one display only.
I'm now thinking how to interface:

- Two steppers (2x 3 out)
- Two glass-scales (2x 2in)
- End switches (2x in)
- Spindle encoder (2x in)
- Handwheel encoder (2x 2in)
- Spindle speed control (1x out)

Total^
6 out
12 in

with a PC. Mesa cards are an obvious choice. I thought I could go with 7I92 but I'm lost with the DB25 daughterboards. Some offer an spindle encoder interface. What is this good for?
I have a mill that also has spindle sensing and this is all wired up on the parallel port using GPIO pins.
Do I need this Mesa encoder interface for my application or can I go with the GPIO as well?

Thanks,
Malte

Replying myself to check my understanding:

So when using parallel port on my other machine the evaluation of my encoder inputs happens in base-tread. When using Mesa Cards I essentially offload anything that runs under "base-thread" to the card. So any HAL component I wish to use needs to be supported in hardware.
The other GPIO pins interface only with the "servo-thread" with a limited time resolution.

Is this correct understanding?

Thanks. I think I understand. So I' need

Output
2x stepper (fast)
1x PWM out

Input
5x Encoder input (fast)
2x End switches (slow)

Which would require a 7I77 for the encoder inputs and a 7I78 for step/dir.

The other option would be to go for Machinekit with the BBB (but this is probably the wrong forum for this?)

BR,
Malte

If you need 5 high speed encoder inputs plus step/dir outputs,
it gets fairly expensive with Mesa hardware since there is no single card
solution (there is a single Ethernet card for this but its not supported yet)

You might be able to get away with a dual parallel port only setup if your
step rates and encoder resolutions * axis speeds are not too high.

Yes that was also my assessment. This setup would be expensive to realize using Mesa.
I'm looking at the BeagleBone Black and MachineKit now which has own challenges to overcome (mainly around GUI)