Thanks for the info At the moment I've got a Beagle Bone Green and a Rpi3 handy so I'll probably try both out and use the BBG as the "Gold standard" to check for differences in timing / jitter using a scope. I'll also see if I can get machinekit working under a 64bit os just for fun on the Pi3
I'm afraid the Pi3 still uses Ethernet via USB so that's not great. For the hardware I've got a small ooznest Ox CNC, belt driven with a 1.5Kw spindle / Nema23's At the moment it's running a Arduino Due / RADDS board / TinyG (G2Core) / REPS128 stepper drivers but with no end stops I've also got access to a larger version of the ooznest Ox at the hackspace in manchester, that one uses a GRBL board. I'm thinking of writing my own front end using .Net Core (doesn't require mono) and javascript. Although I'll need to dig into the API's to figure that one out Many Thanks Richard On Tuesday, December 19, 2017 at 4:25:27 PM UTC, Ric W wrote: > > Hi, > I've recently been looking into setting up my own CNC Electronics. > > The first question I've got is over latency performance. > I know the Beaglebone AM3358 has a single core 1Ghz Arm Processor and 2 x > PRU's running at 200Mhz > For the Rpi3 it has a quad core 1.2Ghz Arm Processor - BCM2837 - A53 > > Now I know that one of the ways machinekit gets low latency is to use the > PRU's for dedicated motion control on the BBB. > But I was wondering if the Pi3 had one of it's cores dedicated to the > Operating system and the other 3 somehow dedicated to motion control then > how would this compare. > One difference the PRU has is that it's instructions take 1 cycle to > complete, but on the other side the Pi3's other cores are running at around > 1000Mhz faster with 3 available. > Is this a supported setup from machinekit's point of view (has someone > already done this?) > > The next question I've got is regarding hooking up the control board to > seperate stepper driver boards etc. > I know one of the downsides of an Rpi3 is the GPIO count, so I started > looking into different options > I liked the look of EtherCat but I think there's no open source hardware > shields > and most of them just appear to use a netX52 to fire SPI data over > Ethernet. > Since the boards I'm planning on using will all be in the same shielded > case I figured I might just try a shielded SPI cable to each slave board. > > There's some discussion online over what the max SPI speed is for an Rpi3, > theoretically 125Mhz although I've not tested that yet. > My plan is to use some TMC2660 Stepper drivers that can give a smoother > waveform (quieter) > and provide feedback on the amount of force the stepper motor is using, > with an auto cut off if the force goes over a certain limit. > > If I were to try something like this then I'd guess I'd have to write some > custom HAL modules etc. > But I wanted to get any comments first from the folks here as to what > they're thoughts might be for the hardware. > > Also btw I think the search box is broken on the machinekit website > > Many Thanks > Richard > > -- website: http://www.machinekit.io blog: http://blog.machinekit.io github: https://github.com/machinekit --- You received this message because you are subscribed to the Google Groups "Machinekit" group. To unsubscribe from this group and stop receiving emails from it, send an email to machinekit+unsubscr...@googlegroups.com. Visit this group at https://groups.google.com/group/machinekit. For more options, visit https://groups.google.com/d/optout.
