raw i/o with linuxcnc will do almost everything that the external hardware will do.. You are just limited by how fast.
so.. Lets say you have a 40000ns base thread. That means the base thread runs at 25khz.. (I have a few i5 machines that seem to do a really good 20000ns thread) Any way.. Lets say you have a 25khz base thread. Encoders - You should be able to approach counting at 25khz if the quadature signal is perfectly 50%. (I might go 10% less) So - at 600 line encoder or 2400 count? The absolute max counting rpm would be 625. steppers.. most (prinnter port and hal_gpio) seems to support reset - which again means you can approach base thread step frequencies.. (minus reset time and stepper timing settings) So - with a 40000ns base thread - you can create close to 25khz step pulses.. Granted - external interface cards (like mesa or pico or such) are way better at generating these signals and way more consistent but the raw i/o still works just fine in a pinch. sam On Tue, Aug 27, 2024 at 6:12 PM Chris Albertson <albertson.ch...@gmail.com> wrote: > > > > > So you are right, the ARM family is likely more than fast enough for > > trajectory planning and graphical user interface but can it handle the > low > > end hardware? > > My experiance with robotic motion control says “no, it can’t”. But that is > Ok because today no one would design tasks like encoder reading or BLDC > motor comutation into the Linux-based computer. We can buy a Raspberry > Pi Pico for $5 that can do 20 million encoder transitions per second and > program it using either Arduino IDE or (better) in micro-python. Today > what people do is “close the loop” in the microcontroller and the Linux app > only has to send the (time-tagged) target trajectory points, PIOD > constants, and so on. > > The thing about the Pi is not that the CPU is too slow but the > communications bus is very limited. This is mostly fixed on the Pi5 but > still the Pi does not have a 16-lane PCIe bus and there is no way to > install a high-end GPU. The only connection is the GPIO pins and those > are not “high bandwidth”. > > > I think the Pi5 would be good for Linux CNC if you used an > Ethernet-connected Mesa card. The Pi5 has much better networking than did > the pi4. > > ARM is of course the future. Apple moved from Intel to ARM and the rest > of the PC industry is trying to follow. At some point to change-over will > be complete. Buit it should not matter. Today we should be controlling > our machines via standard interfaces such as Ethernet or Thunderbolt (USB > 3/4) or other high speed ports found on every computer. > > > > > > John > > > > > >> -----Original Message----- > >> From: Todd Zuercher via Emc-users [mailto: > emc-users@lists.sourceforge.net] > >> Sent: August 27, 2024 12:50 PM > >> To: Enhanced Machine Controller (EMC) > >> Cc: Todd Zuercher > >> Subject: Re: [Emc-users] LinuxCNC 2.9.3 has been released > >> > >> I have no experience with the Pi. But I've been of the opinion that > > computer > >> horse power has not been a real issue for Linuxcnc for a very long time. > > A > >> pc's real time latency generally has (or used to have) little to do with > > how > >> fast the computer actually is. It is more about the whole of the > > computer's > >> architecture. Back in the day we were running EMC2 on pcs with Pentium > > III > >> and Pentium 4 cpus with respectable latency and adequate speeds. Even a > >> Pi3 is probably at least as fast or a faster pc than most of those old > > dinosaurs. > >> > >> As long as a computer has enough processing power and resources to > >> comfortably meet the host operating systems requirements, it will be > fast > >> enough to run Linuxcnc, so long as it can also reliably meet the > real-time > >> latency requirements. Or at least that was the case with older RTAI > > kernels. > >> The newer Preempt-RT ones do seem to be more reliant on processing power > >> to get decent latency. I believe that may be because it is more of a > > patch > >> within the kernel vs RTAI which is more on the outside. > >> > >> Now to my uninformed mind it appears to me that ARM cpus would have a > >> strike or two against them when it comes to real time. (But I have no > > idea if > >> that is actually true or just my own personal misconception.) My > thoughts > >> being that an ARM cpu operates in more of an indeterminant manor than a > >> CISC one. True ARMs are used all the time for real real-time > > applications, but > >> those are generally using a dedicated real-time os to do singular tasks, > > not > >> trying to do real time within a threaded PC environment. If this isn't > > the > >> case would someone more familiar with the inner workings of computers > >> please set me straight. > >> > >> All that said, Pi3s have already been proven to work at least > marginally, > > Pi4s > >> to work adequately, and Pi5s???, but there's no evidence to expect less > > than > >> the Pi4. > >> > >> What was the question again? And why did I type all this? I'm just > going > > to > >> click send rather than delete, to try to justify my wasting of time. > >> > >> Todd Zuercher > >> P. Graham Dunn Inc. > >> 630 Henry Street > >> Dalton, Ohio 44618 > >> Phone: (330)828-2105ext. 2031 > >> > >> -----Original Message----- > >> From: John Dammeyer <jo...@autoartisans.com> > >> Sent: Tuesday, August 27, 2024 12:38 PM > >> To: 'Enhanced Machine Controller (EMC)' < > emc-users@lists.sourceforge.net> > >> Subject: Re: [Emc-users] LinuxCNC 2.9.3 has been released > >> > >> [EXTERNAL EMAIL] Be sure links are safe. > >> > >> I've read a posting on another forum where the author states he's > running > >> LinuxCNC with a Raspberry Pi using the Pi4 (and now Pi5) I/O pins > > configured > >> to duplicate the PC parallel port. With the quad core processor on the > Pi > > is it > >> now fast enough to duplicate a PC with a parallel port or is the guy > full > > of BS? > >> John > >> > >>> -----Original Message----- > >>> From: Chris Albertson [mailto:albertson.ch...@gmail.com] > >>> Sent: July 13, 2024 11:40 AM > >>> To: Enhanced Machine Controller (EMC) > >>> Subject: Re: [Emc-users] LinuxCNC 2.9.3 has been released > >>> > >>> If the old Lenovo PC has ahard drive, or better yet an SSD inside,then > >>> it will run much better then the Pi4 that is runniong off an SD card. > >>> Those cards a re very slow. > >>> > >>> If you want to upgrade the hardware replace th mechanical hard drive > >>> in the PC with a SATA SSD. If it already has an SSD, then you are > >>> good already > >>> > >>>> On Jul 13, 2024, at 11:24 AM, John Dammeyer > >> <jo...@autoartisans.com> > >>> wrote: > >>>> > >>>> > >>>> > >>>>> From: andy pugh [mailto:bodge...@gmail.com] > >>>>> > >>>>> On Sat, 13 Jul 2024 at 19:00, John Dammeyer > >>>>> <jo...@autoartisans.com> > >>>>> wrote: > >>>>>> > >>>>>> Hi Andy, > >>>>>> On my workbench for playing around I'm running 2.8.4 on a Pi4 with > >>>>>> an > >>> LCD > >>>>> touch screen and the MESA 7i92H. How easy to update that? > >>>>> > >>>>> The best thing to do with a Pi is probably to make a new SD card > >>>>> from the LinuxCNC image, then copy your existing config across > >>>>> (probably easiest to put the linuxcnc folder on a USB stick then > >>>>> swap SD cards) Then you can always go back to the old, working, SD > >>>>> card if there is a problem. > >>>>> > >>>> > >>>> Thanks. That's what I figured. > >>>> What about the 2.8.1 PC? Better to replace it? I picked it up > >>>> surplus for > >>> about $75 a number of years ago. I have a second one as a spare. > >>>> John > >>>> > >>>> > >>>> > >>>> _______________________________________________ > >>>> Emc-users mailing list > >>>> Emc-users@lists.sourceforge.net > >>>> https://li/ > >>>> sts.sourceforge.net%2Flists%2Flistinfo%2Femc- > >> users&data=05%7C02%7Cto > >>>> > >> ddz%40pgrahamdunn.com%7C4a116847897741b4963608dcc6b6d4c4%7C5 > >> 758544c5 > >>>> > >> 73f47cebee96c3e0806fb43%7C0%7C0%7C638603735784920972%7CUnkno > >> wn%7CTWF > >>>> > >> pbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXV > >> CI > >>>> > >> 6Mn0%3D%7C0%7C%7C%7C&sdata=fj%2FKIo6UJD7KW3xxD2WCJ%2BPLkh6 > >> ZxRoVLUlYs > >>>> vkv%2FIc%3D&reserved=0 > >>> > >>> > >>> > >>> _______________________________________________ > >>> Emc-users mailing list > >>> Emc-users@lists.sourceforge.net > >>> https://list/ > >>> s.sourceforge.net%2Flists%2Flistinfo%2Femc- > >> users&data=05%7C02%7Ctoddz% > >>> > >> 40pgrahamdunn.com%7C4a116847897741b4963608dcc6b6d4c4%7C57585 > >> 44c573f47c > >>> > >> ebee96c3e0806fb43%7C0%7C0%7C638603735784932012%7CUnknown%7 > >> CTWFpbGZsb3d > >>> > >> 8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0% > >> 3D%7C > >>> > >> 0%7C%7C%7C&sdata=CD%2FxKbSxVj%2BQX7cSM8JceD%2BG%2FQAKCzYmq > >> a5aM3QKAWo%3 > >>> D&reserved=0 > >> > >> > >> > >> _______________________________________________ > >> Emc-users mailing list > >> Emc-users@lists.sourceforge.net > >> https://lists.sourceforge.net/lists/listinfo/emc-users > >> > >> _______________________________________________ > >> Emc-users mailing list > >> Emc-users@lists.sourceforge.net > >> https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
