[jeffrey001]

I got this error many times tonight, what does this mean?

At the same time, I get this one too.
USB device(CP2101_USB_to_UART_Bridge_Controller)was plugged in

And this one too.
USB device(CP2101_USB_to_UART_Bridge_Controller)was unplugged in

When this happens, I have to reset and start again, don't need to reboot

Thanks for any help

[jwatte]

This probably means the USB connection between the board and the computer is seeing interference. That interference was bad enough that an attached board/device behaved as if it was un-plugged and then re-plugged. And, doing so, the computer couldn't talk to that device ("unrecoverable IO error")
You may be able to make it better with a higher-quality USB connection cable, or by clamping an RF blocking bead across the cable.
If that doesn't work, you have to figure out where the interference is coming from (typically large relays/contactors going on/off) and add filtering there.

Note that Tormach uses the term "USB board" for things like the Z-cool and the ATC. Which attachments do you have to the controller?

It could also be a power or grounding issue, that causes the device to detach and re-attach; again, good cables should be able to reduce the incidence of that problem.

That being said, USB is not a great industrial-level bus, because it is not engineered for robustness in these situations. This is why "real" industrial systems often use something like CAN or RS-485, which are slightly heavier-weight connection standards. But USB devices are very cheap and easy to add to an existing computer, and it does both signalling and power in a simple cable, so I can understand the appeal.