Stepper drivers and breakout board

[Neale]

I'm a bit confused about whether you are going to drive the machine from Arduino or a PC. Is the plan to start with Arduino and move to PC (Mach3 or LinuxCNC) later?

Anyway, if you are using the Arduino, you don't need a breakout board. The Arduino output pins will drive the stepper drivers (AM882 or whatever) directly. I've used an Arduino with a terminal strip "shield" running grbl with a TB6600 with just wires between them. Driving an AM882 is just the same.

With a PC, you need a breakout board. The simplest ones are little more than terminal blocks which split the set of connections in the parallel connector to separate terminals for easier connecting. There will probably be some simple electronics (opto-isolators) as well to provide a bit of protection between the PC and the stepper drivers but in essence, the BOB is a fancy terminal block.

If you use Ethernet, this device will only work with (probably) Mach3 and needs driver software added to mach3 to take the signals that would have gone to the parallel port and convert them into Ethernet data in some proprietary format for that specific Ethernet "BOB". Even if you have an Ethernet shield for your Arduino, it will not talk to that Ethernet BOB - but there's no particular reason to use it as you can connect directly (as above) and the reasons why you might go to Ethernet using Mach3/PC don't really apply.