On Thu, 23 Dec 2021 at 00:50, Tixy <[email protected]> wrote: Hi Tixy,
After reading your several musings in this thread regarding USB verses serial interfaces for CNC machines (3D printer, etc), I thought I'd respond, because I think they are missing the mark. > I guess it's possible to use a USB to serial chip in the > printer which then talks to a serial interface on the computer driving > the printer. But that is very clunky ... I have a budget 3 axis CNC router and that's exactly how it operates. Apart from that, I'm not involved with the CNC world, but I get the impression that this is standard practice at all scales, for historical and practical reasons. I'd suggest that this is because for CNC applications, USB is not better than a UART serial interface, and probably worse. So CNC machine designers would have begun with serial interfaces before USB was invented, and then had no reason to change to USB. Reasons that occur to me: - USB has poorer noise immunity (don't forget that a CNC machine contains several motors and is often used in industrial settings which can be electrically noisy). And in CNC, anything going wrong typically produces some kind of disaster of a catastrophic, unsafe and expensive nature. - USB has maximum cable length specification of only a few metres (so wikipedia says). - USB is optimised towards higher data rates. In general a CNC machine receives one small file of G-code, and then autonomously fabricates an item. It is irrelevant if the file transfer takes seconds, when the mechanical job takes minutes. - CNC machines aren't mass consumer items, so they don't need to follow fashion.
