Hi Sam, I'll address your comments and also Gene's. Back in 2005 when I started the ELS project I was looking at using a TI DSP for the core processor and it had hardware quadrature support but the infrastructure to write software and program it put it out of reach for most of the people on the E-Leadscrew forum. So I changed to a Microchip PIC series with free IDE and C compiler and went to 1 PPR because back then often even a used encoder was as much as $400 not to mention toothed pulleys and belts weren't priced the way they are now with everything including custom cheap PC boards from China. The article in Circuit Cellar Ink magazine (Nov. 2006) talked about some of the issues and since MACH2 (MACH3 came a bit later) used a 1 PPR sensor on the spindle for lathe threading it appeared possible.
My Base thread runs 20kHz but I didn't have enough pins available to use quadrature. In hindsight I wish I'd done that differently but still I was able to attain 20kHz step rates even if the motors couldn't do it and most step motor drivers were still running over $100. The original target price of the ELS was $150 and that included a MicroStepper Driver (3A 55V). Fast forward to now and a Microchip PIC32 has the Encoder hardware, USB interface and ability to run a 25kHz base thread. A 1000 line encoder or more becomes easy for a dedicated ELS type project. But why bother when the Pi4 + MESA solution is cheaper and more powerful. It's that which has kept me from upgrading my ELS from the PIC processor to the PIC32. The PIC18 C code translated easily from 8 bit to 32 bit and ran the original ELS hardware including the onboard micro-stepper electronics. (Attached photo shows prototype). Most people are also happy with the electronic gearing where the encoder pulses generate stepper pulses done with an assembled and tested Arduino bought from China for less than I can buy the parts installed on the Arduino from Digikey or Mouser. Therefore 4 years ago I stopped with the ELS upgrade. No one wants it. Be better to just turn the existing ELS into the equivalent of a pendant onto a headless Pi4+MESA LinuxCNC which is possible because the ELS does have an RS232 serial port. However at the moment I don't know how to do that and as I've already seen, once someone actually does get LinuxCNC up and running the desire to drop down to just a simple ELS vanishes. John > -----Original Message----- > From: Sam Sokolik [mailto:samco...@gmail.com] > Sent: August 28, 2024 7:05 AM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] LinuxCNC 2.9.3 has been released > > 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
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