Laptop solutions?

jaguar36 wrote:

All of the hardware seem to hinge on either a native parallel port or a PCI parallel port board. Are there any USB, ethernet, or heck even expresscard based solutions out there?

Parallel port setups are popular for low cost, but obviously offer only very limited pin count and slow update rates. They are not really suitable for a servo system (though it can, just about, be done).

Have you seen: wiki.linuxcnc.org/cgi-bin/wiki.pl?LinuxCNC_Supported_Hardware ? It could do with being updated, I admit.

There are some solutions that use the Parallel port as a data bus. This is a whole different level of capability to using the pins directly, and can offer ample IO pins and fast stepping or fast encoders and analogue outputs. The main player here is Pico Systems:
pico-systems.com/motion.html
Mesa also offer the 7i43 (I use one myself) and the newer 7i90 The latter offers MHz counting/stepping and 72 IO points.

I think that the majority of conversions of larger machines are using a PCI card of some type. Perhaps you have looked at the Mesa 5i25 and mistaken it for a parallel port card? It isn't, it just has a connector that is compatible with parallel port breakout cards. It has on onboard FPGA and it too offers MHz IO speeds and can support up to 768 IO points. (though not both at the same time). Mesa have a large range of PCI cards for just about any requirement.

General Mechatronics also offer a PCI-card based solution for LinuxCNC www.generalmechatronics.com/en/linuxcnc

LinuxCNC will never be able to work with USB. The USB protocol simply allows too much latency. The only way round this is to put the motion controller on the USB card, which is what Smoothstepper does. LinuxCNC is a motion controller, it makes no sense to use it to control another motion controller. If you want an add-on motion controller outside the PC then that is the route that Mach4 has taken,and that ought to work OK for you if you definitely want to use USB.

There are Ethernet based options too. For a stepper system the Mesa 7i76E is becoming popular. but there are other options for servo systems that use more than one card.

jaguar36 wrote:

Has this been looked at in the last 5-10 years? USB 3.0 allows for some very low latencies, in the 20us range.

I am not a hardware developer, so I have no idea about the answer to that question. But I suspect that the answer comes down to the differerence between best-case latency, worst-case latency and theoretical max allowed latency.
A quick Google search found one set of numbers giving 1.3mS latency for USB3 but whether that was a relevant test is not something I can tell.

This looks like it would work well, I thought linuxcnc's Ethernet support was still in the experimental stage though?

It will work well if you machine is stepper-based. If you have servos then there are better choices.
Ethernet cards are supported in the released version (2.7) of LinuxCNC if you install the "uspace" variant, so are now more "new" than "experimental".