On 22/12/17 06:55, Alexander Rössler wrote:
If you are planning to write the GPIO drivers yourself, you might also
consider the OIDROID C2, as reported here
https://github.com/machinekit/machinekit/issues/1269 it has very low
latency.
Yes see entry at
https://github.com/machinekit/machinekit/issues/1269#issuecomment-326965404
The main problem I had with getting machinekit to build on a Pine64 was
the lack of an io.h header.
Mine was not an elegant or definative solution, but it worked.
Don't doubt you could come up with a better solution, looking at
removing the unsupported low level functions from
an aarch64 build would probably be a better tactic:-)
But, we do not officially support aarch64 yet. Nevertheless, I would
love to see it working.
'Ric W' via Machinekit writes:
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
You might also want to check out Machinetalk:
https://machinekoder.com/machinetalk-explained-part-1-introduction/
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
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