Connecting to a CNC machine, pros and cons of USB vs PP vs Ethernet etc.

[m_c]

Would you pair put the handbags down! :)

In terms of Mach3, Ethernet is the more reliable communication method for external motion controllers.
The reason for this, is Mach3 can't handle any errors or glitches in the communication method.
Ethernet handles errors and glitches at a hardware level, it's also an isolated system, so is much more tolerant of external noise, and should a packet fail to reach it's destination, the hardware (ok, it's technically the embedded code in the Ethernet controller if you want to split hairs) will handle the problem and resend it until it reaches it's destination.
USB doesn't have that, so any packet of data that gets corrupted, has to be detected and handled by software. I'm sure if the plugins could be designed to do this, they would, however it's one of the things that Mach3 was never designed to handle, as it was originally written to talk directly to the parallel port.
I think it would be fair to say external motion control, was simply patched onto the Mach3 core.

One key point to remember, is once you involve Ethernet or USB, you are no longer running realtime. All you're essentially doing is running a faster version of ye olde RS232, in that you send commands to a controller, and the controller (hopefully) tells you it's been done.


However, USB can be used reliably. I run several KFlops, and they are far more stable than my USS ever was with Mach3. My lathe still occasionally locks up Mach3 (my manual lathe is the sole trigger for this!), but no where near as often as the USS ever did.
I am in the process of moving to KMotionCNC, as it can handle communication problems far more gracefully (and it has less issues, but that's for another topic!), and will happily resume once things are back to normal.

[JAZZCNC]

Would you pair put the handbags down! :)

However, USB can be used reliably. I run several KFlops, and they are far more stable than my USS ever was with Mach3.

No my Hand bag is always read for Action.!!. . Lol

Now Come on M_C we both know you are talking about a very High quality product when using Granite's Kflop controller it's not your average USB Mach3 controller.
The point I was making in first place is that USB isn't stable as Ethernet when used with Mach3 which we know thru experience is true. We Have Both pulled our hair out with USS(USB Smooth Stepper for those we are wondering.!!) and I've done much the same with every other run of the Mill USB controller for Mach3.
Ethernet on the Other hand is another ball Game. Classic example is the Pokeys 56/7E and now 57ECNC which do Motion control they are cheap and work great they never Miss a beat. The 56U on the other hand was a pain when used for motion control with Mach3, mainly I think because it relied on USB for 5v but still it couldn't be trusted.!

USB driven card Isn't ok for Motion control unless your prepared to spend on quality devices like Granite's Kflop etc so to me it's not for the average DIY user and best avoided.! And now with Ethernet devices coming more available at sensible money what the point.!