True, all USB devices, the USB SmoothStepper included struggle to deal with electrical noise in an industrial environment. The Mach3/SmoothStepper combination makes this particularly painful because a communications hiccup usually results in having to restart Mach3 and sometimes even requires a power on reset of the SmoothStepper to force Windows to reinitialize the protocol stack.
Regular USB does not provide galvanic isolation and ground loops are a real NO-NO because current flowing in the shield of the USB cable will corrupt the data. There are USB isolators, but the results seem to be mixed on their success. I suspect that this is because isolation alone may not solve all the noise problems. Ethernet mostly solves the electrical noise problems. The Ethernet protocol stack in Windows does not try as many queuing tricks as USB and the response is much better. Use of the correct modes can bypass the error recovery stuff in the protocol stack that causes delays when the delay results in more problems that the lost data would cause. Most of the issues with Ethernet are with addressing and firewalls. Steve Stallings > -----Original Message----- > From: Dave Cole [mailto:linuxcncro...@gmail.com] > Sent: Friday, February 28, 2014 10:48 AM > To: emc-users@lists.sourceforge.net > Subject: Re: [Emc-users] Printrboard and LinuxCNC > > The original Smooth Stepper also suffered from USB issues > which seemed > to be related to grounding or isolation issues?? > > Steve probably knows a lot more about that than I do. > > The later designed, Ethernet Smooth Stepper device does not seem to > exhibit similar issues. > > Dave > > > > On 2/28/2014 10:32 AM, Steve Stallings wrote: > > Andy's description of the Mach external pulser API > > is correct. > > > > The device driver gets to select the length of the > > buffer and also select a "pulses per time slice" > > or a way-point version of the data. > > > > USB under Windows seems to require at least 1 second > > of buffered data to be workable. Not pleasant, but > > lots of people use it anyway. USB itself is not the > > problem, it is the Windows protocol stack that can > > cause significant delays. It is optimized for throughput > > not minimum latency. > > > > E-Stop, limits, homing, probing, and threading are the > > responsibility of the device and its driver. This results > > in lots of complicated code in the driver and significant > > variations in performance from one type of device to another. > > > > Steve Stallings > > > > > > > > > >> -----Original Message----- > >> From: andy pugh [mailto:bodge...@gmail.com] > >> Sent: Friday, February 28, 2014 8:52 AM > >> To: Enhanced Machine Controller (EMC) > >> Subject: Re: [Emc-users] Printrboard and LinuxCNC > >> > >> On 28 February 2014 13:36, Michael Haberler > >> <mai...@mah.priv.at> wrote: > >> > >>>> The question, then, is how come Mach3 can have USB > >> cabling, but LinuxCNC > >>>> can't? (see the KX* mills from Arc Eurotrade in the UK; > >> now with USB input) > >>> I have no idea about that API uses over USB, but I'd be curious > >> There is a clue on page 26 here: > >> > http://www.warp9td.com/documentation/SmoothStepperUserManualV1.0.pdf > >> > >> It looks like the SmoothStepper accepts 1kHz position data, rather > >> similarly to the Mesa and Pico boards. The difference seems to be a > >> buffer of around 1 second. > >> I assume that e-stop (at least) is handled on-board. I > rather assume > >> that limit switches and homing need to be too. > >> > >> -- > >> atp > >> If you can't fix it, you don't own it. > >> http://www.ifixit.com/Manifesto > >> > >> -------------------------------------------------------------- > >> ---------------- > >> Flow-based real-time traffic analytics software. 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All-in-one tool. > http://pubads.g.doubleclick.net/gampad/clk?id=126839071&iu=/41 > 40/ostg.clktrk > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Flow-based real-time traffic analytics software. Cisco certified tool. Monitor traffic, SLAs, QoS, Medianet, WAAS etc. with NetFlow Analyzer Customize your own dashboards, set traffic alerts and generate reports. Network behavioral analysis & security monitoring. All-in-one tool. http://pubads.g.doubleclick.net/gampad/clk?id=126839071&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
