Raspberry Pi 2

The new Raspberry Pi 2 will have Ubuntu as a possible OS. It sounds like it there is a chance it could be a LinuxCNC controller candidate.

Initial thoughts? Any devs going to give it a try?

It has already been mentioned on the Machinekit forum.

That is where it is most likely to be used, but not with Ubuntu, with a slim install of Debian and a Xenomai kernel.

regards

It could work in userspace, but that needs lot of testing and would be limited to only stepgen.

I think really needs a RT kernel so that a reasonable constant time servothread is available, I doubt any RT kernels will be available for a good few months.

I may give it a try next year or when I see RT kernel patches available.

Really though not sure why I will bother as its only a slightly cheaper beaglebone without PRU or analog IO, possibly its better for most people to look at using beagle machinekit.

I have heard beagle will do 1MHz step rates, rpi1 could almost push 100kHz(there are possible ways to use VC4 for higher but huge amount of work required) but then running other stuff in python slowed to unusable, my guess is the rpi2 has plenty of speed for even 2MHz step rate and plenty of cycles left for opencv python processing.

I am guessing if computer vision is required maybe rpi is better, really depends what requirements are.

I will if I get time try and put out something for the rpi1 soon, unfortunately everything always seems SNAFU for me and I still have to get a dev system setup after a harddrive crash.

The 3.18 RT_PREEMPT kernel patches are surprisingly already available.

If a decent kernel can be patched and run then machinekit should compile no problem.

I compiled machinekit on the rpi2 last weekend with posix threads, which is only an hour or so of messing about on the rpi2, but, getting a good RT kernel is probably 3-4 weekends worth of hacking unless it just works.

Unfortunately I don't have a suitable environment for cross compiling and am to busy with other things to want to try a kernel compile for a few weeks anyways.

If anyone gets a good RT_PREEMPT kernel compiled please post links there I will give it a try.

I though I was not going to bother trying a kernel compile as I do not have a working x86 system of any power tat I could do a cross compile on, but I decided to give kernel compile a go on the rpi2 yesterday.

Results look really good.

running 'time make -j4 zImage' completed in 28 mins
Installed RT kernel and it worked first time with no visible problems, run linuxcnc compiled for ARMv6 with no problems.

cyclictest seems to show 3-4 times latency improvement on the rpi1 with even opening all the major apps while running cyclictest (epiphany, Mathematica, sonic pi, and glade) and non of the apps seemed particularly sluggish.

I did a few other loop tests and I am guessing that 200us servo thread and 200ns virtual base thread could be easily possible just running on the ARM.

Unfortunately the old rpi DMA and vc4 optimized drivers will not work and I guess that is about 1-2 weeks work to fix.

If I try and work on it every weekend from now on maybe could have a working system in 4 weekends of work (wishful thinking).