Confused about hardware to get

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08 Sep 2021 18:38 #219984 by 109jb
I have a RF-45 type bench mill with 3-axis closed loop steppers. Up until now I have been using GRBL on an Arduino combined with an old netbook for control. The steppers and home/limit switches are connected to a parallel port breakout board which the Arduino feeds through the parallel port connection. This system has work OK so far and I would say it is good for what it is; however, I am to the point where I want more that GRBL can provide. I had another bench mill that I used an old desktop running LinuxCNC and want to get back to LinuxCNC. I'm not looking for MHz performance. GRBL is limited to 30 KHz step rate which is ok for me and my use. What I would like to achieve is being able to have the canned cycles, cutter radius compensation, probe input, possibly 4th axis, and MPG support that LinuxCNC can provide. I don't think I need spindle control. I'm a hobbyist, so I wind up making a lot of one-off parts and sort of "manual" machine them using MDI where I think I could do about as well and easier with a MPG. I don't mind spending a bit of money for something like a MESA card but want to stay away from the huge desktop solution. Here is what I envision:
  1. 10 to 15 inch display Could be HDMI or VGA, don't care, but I do have a few 15" LCD monitors available.
  2. MPG - Would do either wired or wireless, USB, or whatever works type connection.
  3. Some kind of single board computer. I have been looking at the Rock  Pi X which is a X86 SBC with Atom processor, but not locked in. Could be a Raspberry PI, or whatever
  4. Ethernet MESA card or similar.
  5. Mount all of the above to a arm on the side of the machine
So my confusion is what works and would be the least painful to set up?  This leads to the following questions:
  1. Is there a SBC that is easiest/proven? The Rock Pi X seems like it is pretty well tested in terms of running Linux although not specifically the LinuxCNC distro.
  2. Which MESA or other ethernet card would fit running 4 axes, home/limits, probe etc. as described above?
  3. For MPG, I see MPGs that are USB, but do they work with LinuxCNC. Any recommendation for a specific MPG would be appreciated.
Finally are there any tutorials or guides for using or setting up a SBC based system?

Thanks,

​​​​​​​John Brannen

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08 Sep 2021 19:02 - 08 Sep 2021 19:14 #219989 by Aaroncnc
There are a few guides to use SBC for linux cnc.
The RPI4 has shown it self decent.

there are 3 ways to use it listed from slowest to fastest and also cheapest to most expensive.

Use the built in gpio
Use Remora remora-docs.readthedocs.io/en/latest/index.html (this is the option i have gone with, But the best board with the lpc chip is hard to get right now with the current supply problems. a new version for the stm32 based chips is being worked on but not yet ready. )
Use a Mesa card, can be SPI (store.mesanet.com/index.php?route=product/search&search=rpi) or ethernet based.(store.mesanet.com/index.php?route=produc...rt=p.price&order=ASC)
Last edit: 08 Sep 2021 19:14 by Aaroncnc.

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08 Sep 2021 19:16 #219991 by Aciera
Using a Raspberrypi 4 with a mesa ethernet card (eg 7i76e) would probably be the path most travelled.

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08 Sep 2021 22:14 - 08 Sep 2021 22:14 #220013 by 0x2102
I would probably stay away from a RPi4 and get a used Lenovo Tiny M73 or M93 on eBay + Mesa 7i96 or 7i76e if you need more I/Os.

Linux Mint 19.3 Mate Desktop as the base OS.
forum.linuxcnc.org/9-installing-linuxcnc...nd-easy-installation
Last edit: 08 Sep 2021 22:14 by 0x2102.

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08 Sep 2021 23:02 #220014 by Aaroncnc
I would say a used desktop plus mesa is the right solution.
I know which my dealing with the rpi4 the open gl support is limited and it makes it hard to use some gui's

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08 Sep 2021 23:44 #220019 by 109jb
Thanks everyone for the suggestions so far. Turns out I have a RPi 4 that is my sons here at the house that I can try but the SD card image on the Getting LinuxCNC page says it won't work on an 8GB RPi. Since I have this RPi sitting here I would like to slap it in and see if it will do anything. Is there any image out there that will work on the 8GB RPi?

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09 Sep 2021 00:25 #220020 by Aaroncnc
You should be able to use the 8GB image but you have to limit the ram to 3gb.
There should be a thread on here about the command to limit the ram.

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09 Sep 2021 01:20 #220023 by 109jb
I actually found one that worked right off the bat. Did a little searching and came up with this post by user @elovalvo.

forum.linuxcnc.org/9-installing-linuxcnc...-2gb?start=50#206085

His image loaded on my sons RPi and booted right up. I skipped the updates for now but it is working running Axis in simulator mode.

Now to see if any of my 15" monitors are HDMI compatible and decide on a Mesa card. I'm leaning toward the 7i96
store.mesanet.com/index.php?route=produc...rt=p.price&order=ASC

Do you folks think the 7i96 is adequate given the description in my first post? 

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09 Sep 2021 02:00 #220026 by Aaroncnc
to be honest i dont have much idea on mesa cards,
But i think for your setup it should be fine.
The main concerns are number of axis and inputs and outputs.
5 Axis
11 isolated inputs
6 isolated outputs
A high speed encoder interface is provided for spindle synchronized motion

This would get you everything plus some from your post.
The high speed encoder would allow you to do rigid taping.


I would hope someone with more hands on knowledge of the MESA card will chime in to confirm.

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09 Sep 2021 20:11 #220080 by Micromachining
Hey John,

before spending some money and nights of set-up. you know grblHal does everything you listed. and will most likely run on what you already have. I have one of everything Mach3, linuxcnc, Grbl, GrblHal, DDCSV, SMC-5, Acorn.

The fastest/smoothest machine i have is running GrblHal and can deliver 500khz per axis, backlash, probing, canned cyc, ATC, mpg 5axis TCP., Spindle control with ridged tapping, etc, it actually has more out of the box the LinuxCNC and is way easier to set up. Look up GrblHal and IOsender

Dont get me wrong I love my LinuxCNC/Pathpilot. LinuxCNC can be configured to control anything and do it well. but Its not the easiest to get going or even the best bang for you buck. check out Teensy 4.1 cnc 40 bucks gets you a ripper of a system

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