Linuxcnc on Raspberry

Surely the Beaglebone is a better platform for cnc comapred to a RPi ? I'm interested in the advantages of an RPi over a BBB.

I'll concede the machinekit is the only option for the BBB, but there's 35 lines available for I\O and that's with keeping video, hwd stepgen without having to add any other hardware, the level shifting is a doodle to implement. And the BBB is open source, if that is important.

I chose the BBB over a x86 platform, but I'm kinda odd.

ozzyrob wrote: Surely the Beaglebone is a better platform for cnc comapred to a RPi ?.

I have heard that the BBB struggles to handle a user interface. The Pi has a much better graphics subsystem than the BB so does better there.

For IO it is possible to connect a Mesa 7i90 to the Pi using SPI. That gives lots of IO and even better stepping than the PRU.
Of course it adds a fair bit to the cost.

Machinekit seems to typically have realtime running on the BBB with the user interface somewhere else. The fundamental philosophy behind EMC (which eventually became LinuxCNC) was to have everything running on one off-the-shelf computer. Machinekit seem to have decided that this isn't the way to go now that there are off the shelf devices like BBB and so see it as desirable to split realtime and User Interface between two (off the shelf) machines.

Or at least that is how I understand it. I have lost track of Machinekit over the years.

I haven't had any issues with the GUI, if axis was an issue I'd try another option.

Theorectically the BBB could do SPI with the right driver.

I'm not a big fan of the whole distributed way that MK seems to be going, rather have everything on the one machine......seems to be a bit "Makerish" for me.

Hi
Ozzrob: can You tell what latency did the BBB get as running with latency-test?
Same question to anyone who dealt with RPi. The <200us from start of the thread does not look so exciting, doesnt it?
RPi using external step generation and simple interface might be quite interesting, it is nice to know I can just download the packages now. I will try sometime in the future as there is one RPi in my box.
That board with isa turned out to be athlon xp 2k. I repaired it, and with rtai latency test it was below 1000ns. Using console display, and even pushing keyboard buttons resulted in some spikes. latency-test along with some disk io resulted in max jitter of around 20us. heavy disk IO like with dd makes some spikes... That is with PCI sata card. NFSROOT may be better... That should not be bad if it manages to keep that value - of course without using the AGP or PCI video (similar results). UPDATED: Now i'm doing `cat /dev/urandom | hexdump -C` and THAT is below 20us. Maybe the console is ok and the hdd makes more trouble
From the results page in wiki, it seems not many PC systems went below 10us. Is anything seriously more realtime?

To tell the truth I haven't run any latency tests with my BBB. I just used an image with Machinekit preinstalled and am using the on board PRU (basically the BBB has 2 separate mcu's that aren't touched by the OS, for those that aren't aware), which gives a kind of hardware step generation, not as good as an FPGA but better than the main CPU doing software step generation.

Best results I've had (below 10K) are
Asus M4A785D-M PRO with an Athlon II x2 250, 4GB ram, Kingston 120GB SSD and on board video.

Asus M2N68-AM-PLUS with an Athlon 64 X2 5200+, 4GB ram, Kingston 120GB SSD and a Radeon HD5450 card.

Asus A8N-SLI/A8N-SLI Deluxe with a Athlon 64 3800+, 4GB ram, Kingston 120GB SSD and a Radeon HD5450 card. (MB & CPU were a dumpster find, have spent the last 5 years running as a file server, I upgraded only cos I wanted to run gitlab)

The first 2 Boards are uATX which better suit my build. Although no ISA slots.

All tests were done with an install of Linuxcnc 2.7 upgraded to 2.7.13. I set the disk up for dual boot, one install with RTAI kernel & and the other with a PREEMPT kernel. The M4A785D-M PRO run just a smidgen under 10K even with the PREEMPT kernel with a servo & base thread. An SSD with 3Gbps or greater SATA port is a game changer. The last two combos with an IDE drive were still well 20K. In all Tests I had sound disabled, which makes a difference and the usual BIOS tweaks.

please any one help me ..?


i am very tired to findout how to install linuxcnc on raspberry pi 3b+.. i was found so many link and step but all these are not work ,so please any one of them tell me how to install step by step linuxcnc on raspberry pi..


thanks you
best regards
Shailesh singh.