I was reading earlier here while searching about a comparison between USB2 and Parallel port interface speed. I realize that through a USB2, information has to go through a processor and more to make it to the motor drives where as the Parallel port is more of a direct connection and just as fast or possibly a faster path to the drives and motors. My question is; is there any truth to the USB2 being better or faster then parallel port interfaces. Thanks, just a discussion.
The throughput of a USB2 is much greater than that of a Parallel port. However from a real-time perspective, which is what counts when doing machine control, a USB port is not a reliable mechanism i.e. you can't count on the timing. Any CNC machines or controllers using USB have buffers and/or on-board processors to take the data stream and feed it out with the proper timing (e.g. smoothstepper).