USBCNC communicates between 50 and 150 times per second with the CPU.
During movement small motion segments are addedd to the fifo buffer of the CPU.
This FIFO allows the movement to work continuously without suffering from the timing hiccups of Windows.
The FIFO may never run empty because if that happens the CPU can not continue and the motion will stop abruptly and give a FIFO UNDERRUN error.
A normal USB 2.0 connection handles this communication speed easily.
However, there are PCs with poor USB chipsets that do not reach 150 times per second.
The result may be that a FIFO UNDERRUN arises with such chipset.
The "timeline" Acer PC series are an example of PC with such poor USB chipset.
There are probably more PC's with this problem, in case of a desktop PC you can add a PCI USB card to overcome this problem.
Another reason that the USB communication can fail is because of EMC noise.
Equipment near the CPU that can cause interference if the electronics cabinet does nut fullfill the EMC requirements.
A VFD (inverter) is often a major source of disturbance.
Switching on/off a motor or transformer or fluorescent lighting can also cause interference.
The manual has an appendix that provides tips on the hardware composition.
Important issues here are:
- metal cabinet
- proper grounding
- proper routing of cables (No spaggetti cabling)
- net filter
- Professional USB cable with double insulation.
See: Hardware Installatie Tips