After much fiddling, I got my BeagleBone Black running LinuxCNC with a
3.8.13 kernel with xenomai real-time patches. Even better, I have
customized Robert C Nelson's imaging scripts so you can download a
ready-to-run version I am calling machinekit.
...and here's a video of going from fresh SD card image to completed
3D print with a few clicks: http://youtu.be/AK_OYoNOBDQ
LinuxCNC really makes a great control platform for motion, and once
the low-level I/O is working you can easily re-configure things using
the HAL, a real-time hardware abstraction layer with tools like PID
controls, filters, ladder logic, etc. In addition, this is a full
Debian development system, with a real-time kernel installed and many
rough edges already smoothed over (although several still remain).
The code is ready to hook to a BeBoPr board and control motors as-is,
but if you want to drive a hot-end and actually print please e-mail me
direct or reply to this post. The temperature logic in the existing
image is crude (at best), and I'll probably have improvements by the
time you get motors moving.
If you need a BeBoPr board, pester Circuitco as to why they're not
shipping, or contact the designer (Bas Laarhoven) who indicated he
still had several on-hand. If enough USA folks are interested, I
might do a bulk-purchase from Bas to save on shipping and get a discount.
Would it be possible to use the BBB, 7" LCD touch screen, & Mesa FPGA cards to get better performance? I have two industrial CNC machines, one I would love to get rid of the controller. That would open up more possibilities for myself. Thank you in advance for any help. (I’m Linux retarded but I have lots of cnc programming experience)
While the promise is there, I don't think that BBB and anything you
can hang off of it is quite ready for industrial control just yet.
Mesa has indicated they are considering products for BBB, but have
nothing ready yet. The BBB could be used as a user interface with a
commodity PC running the machine. This sort of thing is done now, but
it is a lot of work to convert a machine. You might want to look at
the linuxcnc.org web site and get some ideas.
The BeagleBone isn't working with anything from Mesa or any of the
other LinuxCNC hardware add-on vendors just yet. At the moment, I'm
essentially doing software step-gen in the PRU, where I have dual
dedicated 200 Mhz processors to keep the step timings clean.
I have been thinking about and discussing the option of using one of
the parallel port interface boards as an add-on to the BeagleBone, but
that's not going to be working for a while (if ever...it depends
somewhat on manufacturer and user interest).
For now, if you want to retrofit "big iron" and need hardware assist
for encoders, you're better off with a low-end PC platform (like one
of the Atom motherboards) and "conventional" LinuxCNC with the
hardware cards of your choice. You won't regret the extra $50 or so
you spend buying the motherboard and ram vs. a BBB, and on a retrofit
you won't notice the size difference between a BeagleBone and a small
PC. Both will be "lost" in the space vacated by the previous
electronics.
Eric & Charles thank you for the helpful information. I’ll just simplify what I wanted to do and buy a low-end PC. Sounds like that will be the path of least resistance.
