Linuxcnc on Raspberry

Although not the favourite of the Hipster maker communties the BBB is a great SBC platform for CNC combined with Machinekit. The memory thing is a non issue.

The PRUSS makes hardware step\direction a doodle and superior to a Pi solution, MPG is supported by on board hardware.

I use a BBB myself, with a self designed modualr cape, and am more than happy with it.

BrendaEM wrote: Is there something about the Raspberri Pi that makes it heresy to support?

Not at all, and the Pi is supported to an extent. There is even a specific Raspberry Pi driver for the Mesa 7i90:
linuxcnc.org/docs/devel/html/man/man9/hm2_rpspi.9.html

Machinekit has a HAL driver for the RPi GPIO. I am not sure why LinuxCNC doesn't have it too. I have definitely run LinuxCNC on a Pi, and moved motors.

I am using an RPI3 with machinekit driving two PiDiCNC boards for quite some time now, it works nicely without any issues, that is until you load a 4.5MB gcode file, at that point you really get to see the shortcomings of such a system.
Had to change to software GL rendering and it is usable even with those big files.
In general for smaller machines i would use it, as i had no actual problems with it for over 4 months of heavy use.
The real problem with RPI and the likes is to much power saving options that cause to much latency, not the processing power or I/O.

Could the power saving options you described be it throttling from heat?

I wonder how if it would run better on large jobs small heatsink and fan.

It does not help, at least not noticeably. Everything on those boards is made to use as little power as possible, so they have many working states that they keep changing. They can be used with other hardware like the PiDiCNC as the servo thread is set at 1000000 or 1000 iterations per second, but i have mine set at 500000 or 2000 i/s and it works much better.

I've looked at RPis for years, wanting one, but not knowing what do do with it.

Now, I have a 90% completed CNC machine sitting in the garage, ready to hook up to...something.
[I might be able to get an big old power-hungry computer, but it has no video card, and not enough power to run the old GTX 570 just sitting on our kitchen table.]

A friend at our local coffee shop took compiling LinuxCNC raspberry pi as a personal challenge and made this:


I could make breakout board. I was trying to feel out if there was any standard or pin assignments.
I think that any RPI CNC should have realtime clock, so it doesn't need to touch the net.

It would be cool if there was a LinuxCNC/Rasberian distro that can be downloaded, and just sent to a MicroSD.

I feel pretty bad about this. i don't understand why LinuxCNC hasn't really happened on the RPi. GRBL is not flexible enough for my needs, and its code is Atmel only, with no room left on a Arduino. There's no Cnc for the Teensy 3.x, yet. And while I have written sinusoidal stepper algorithms that run on Arduino, I am not sure yet how to do lines over multiple motors.

Configuration-wise LinuxCNC seems very flexible and adaptable, but I wish there was wider support for other computer hardware, such as the Pi.

There is an image of the debian jessie machinekit version floating around the net but it is hard to find.
From my limited experience with RPI, i was extremely disappointed at how miserable the resources for it are, namely you get the RPI all happy and smiling and fire up google to look for an image to write to an SD card and just boot it up to have something, whatever, on the screen to play with aaaaaand after about 2 waisted hours you end up with nothing. Like nothing !!!! Some server images and media server editions exist that work nicely, but for some reason not that easy or obvious to find ( this is from someone who use BBS back in the day and can find damn near anything on the net.).
There are plenty of tutorials, some very nice and concise, some really messed up, but i find it beyond belief that there is so little ready for use for something that has been around for quite some time and supposedly is sold by the millions every year.
As for me i have 2 of them in use, i sincerely doubt i will buy another one any time soon.

tommylight wrote: There are plenty of tutorials, some very nice and concise, some really messed up, but i find it beyond belief that there is so little ready for use for something that has been around for quite some time and supposedly is sold by the millions every year.
As for me i have 2 of them in use, i sincerely doubt i will buy another one any time soon.

Hmm, I did manage to get a Pi to connect to my Solar inverter via Bluetooth and a Power monitor via 433 Mhz radio using a USB TV dongle and push power consumption and solar power generation up to the Internet. That was an interesting project but I don't think I would try it for CNC. And yes, I am not going to buy another one anytime soon. To work with the GPIO was so much harder than using an Arduino.

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.