On Tue, 17 Oct 2017, Chris Albertson wrote:
Date: Tue, 17 Oct 2017 10:41:26 -0700 From: Chris Albertson <albertson.ch...@gmail.com> Reply-To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] Pine64 / Rpi3Latency does not matter if the real-time timing is done on the "far end". N the case where you would use USB or Ethernet you'd have a processor, either an FPGA or a uP. If there is any kind of buffer or memory on the processor then millisecond hang-ups are OK. Proof that this works is with al the machine tools that in fact use these kinds of links. Or just look at anyone who is using an Ethernet connected Mesa card with LinuxCNC. You'd be correct if the far end device was just a dumb serial connected parallel port and all the timing was generated on the PC.
What you say is true of buffered interfaces like Mach/UCCNC/Etc use, It is not true of LinuxCNC where all the critical timing is done in the host. This normally requires at the minimum, reliable communications at the servo thread rate (normally 1 KHz).
The Mesa Ethernet cards are real-time an can support servo thread rates up to 4 KHz on hosts with good real time performance
On Tue, Oct 17, 2017 at 10:25 AM, Peter C. Wallace <p...@mesanet.com> wrote:
On Tue, 17 Oct 2017, Chris Albertson wrote: Date: Tue, 17 Oct 2017 10:02:09 -0700From: Chris Albertson <albertson.ch...@gmail.com> Reply-To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] Pine64 / Rpi3 On the Pi the Ethernet and USB are on the same shared bus. But how much bandwidth is required to drive a Mesa FPGA card? I have read the Ethernet port can only push about 40% of it's spec'd bandwidth but the card only requires 2% it's OK. If performance is the goal you's spend an eatery $50 and buy an Intel PC mainboard rather than the Pi.Performance is not the issue, latency with USB drivers is the issue. USB or USB Ethernet have plenty of performance, but suffer from occasional multi-millisecond latencies. These are fine for normal network usage but not good for LinuxCNCs real time I/O. There are some RPI form factor boards that do have Ethernet built into the SOC which might be suitable for real time Ethernet. On Tue, Oct 17, 2017 at 9:56 AM, andy pugh <bodge...@gmail.com> wrote: On 17 October 2017 at 17:51, Greg Bentzinger <skullwo...@yahoo.com> wrote:> Using > these boards Ethernet port as a dedicated port is an option, I don't think it is. I have heard that the Pi Ethernet port is on the USB bus. -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." ???? George Fitch, Atlanta Constitution Newspaper, 1916 ------------------------------------------------------------ ------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users-- Chris Albertson Redondo Beach, California ------------------------------------------------------------ ------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------ ------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
-- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination.
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