What are our current controller options?

WillAdams
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What are our current controller options?

Post by WillAdams » Tue Mar 31, 2015 11:56 am

Do we have any new options which should be explored / considered?

Gshields are suddenly only available from a single vendor (Inventables) which I was kind of surprised by.

Can Grbl run on an Arduino Mega and drive a RAMPS board? (not as currently compiled / written: http://www.shapeoko.com/forum/viewtopic ... 920#p40409 but there is a project which addresses this: http://sourceforge.net/projects/grblfor ... p_redirect )

Is anyone else comfortable w/ the idea of using a Smoothieboard for milling?

Is the best option really to buy a GrblShield (which uses separate drivers) from Protoneer in New Zealand? or Reactive Substance? Both of those require soldering.... (and use separate stepper driver boards which drives up the cost in the short term).
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lordmundi
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Re: What are our current controller options?

Post by lordmundi » Tue Mar 31, 2015 12:15 pm

Is this an option?

http://blog.protoneer.co.nz/arduino-cnc-shield/

I think it is a shame that these insanely cheap RaspberryPi computers can't be used as a controller directly with some sort of pi hat to interface to the stepper motors. I'm guessing the main difficulty is dealing with not owning 100% of the cpu due to the OS. But this would seem solveable in a couple of ways. One is by programming the pi bare metal, which some folks are doing and would be hundreds of times faster than an arduino. The other possible solution might be the new pi2: its got 4 cores so presumably you could lock down a core talking to the cnc pi hat so that it doesn't get interrupted. Just thinking out loud. It is a shame because they are so widely available, are so fast compared to an Arduino, and are so inexpensive. Not to mention the giant community.

WillAdams
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Re: What are our current controller options?

Post by WillAdams » Tue Mar 31, 2015 12:55 pm

The neat Raspberry Pi option seems to be using an Alamode shield which allows one to directly connect an Arduino (and shield).

That said, I'm probably going to ``borrow'' my son's rPi so as to make my SO3 run headless.
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lordmundi
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Re: What are our current controller options?

Post by lordmundi » Tue Mar 31, 2015 1:02 pm

Right, but that's not exactly but the same thing. I think in that case all you are doing is using it as a way to talk to the arduino that isn't USB. IIUC, it is basically just a gcode sender and the arduino is still the interpreter.

Seeing the struggles with the processing power on the arduinos, and the memory limitation, just think what a $35 pi could do. For one, it could almost any gcode file entirely in memory!

WillAdams
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Re: What are our current controller options?

Post by WillAdams » Tue Mar 31, 2015 1:15 pm

Aren't the Smoothieboards &c. fairly similar to the Raspberry Pi in terms of processing power? Or Beagle Bone Black?

There was a Kickstarter recently for some hopped up BBB which was mostly an increase in processing power (and marketspeak).
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lordmundi
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Re: What are our current controller options?

Post by lordmundi » Tue Mar 31, 2015 2:07 pm

well that's true... my comment focused on the pi or pi2, but you're right... really any of those boards completely dwarf the processing and memory of an arduino. If someone wrote a bare-metal gcode interpreter for them (basically port GRBL over to them), you would have a huge capability increase for about the same cost.

The BBB would have the advantage of having way more GPIO pins, which is always a good thing in the CNC world, and I read something somewhere saying it might be better for real-time development.

Anyhow, I don't know much about this stuff, but as best I can tell, the main reason that people build these interpreters on an arduino rather than something like the pi or BBB is that they have a hard real-time requirement, and an OS on a computer is going to rob you of that (unless you lock down a core or run a realtime kernel or something). Here's a link explaining the issues with controlling stepper motors if you have an non-realtime OS in the loop (this is a great video): https://youtu.be/uIXkvz1-weQ. If you add on one additional step of being able to lock down a core so that linux doesn't run any other processes on that core (which you could do on the pi2), I think you could probably get something running there and get rid of the arduino altogether. Not sure if has enough I/O for a shield or not.

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Re: What are our current controller options?

Post by lordmundi » Tue Mar 31, 2015 2:16 pm

it does look like some folks have gotten linuxCNC running on the BBB, which means it is running either the RT_PREEMPT or the RTAI kernel. that's an option i suppose.

halfnormal
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Re: What are our current controller options?

Post by halfnormal » Tue Mar 31, 2015 3:33 pm

In the for for sale forum a post (spam?) was made for a new controller. http://www.shapeoko.com/forum/viewtopic.php?f=12&t=5817

It looks interesting and uses GRBL. I tried to find any info on the product but looks to be new and of course from China. I do like that the drivers are separate and heavy duty.

I almost bought one just to play with.

WillAdams
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Re: What are our current controller options?

Post by WillAdams » Tue Mar 31, 2015 3:39 pm

halfnormal wrote:In the for for sale forum a post (spam?) was made for a new controller. http://www.shapeoko.com/forum/viewtopic.php?f=12&t=5817

It looks interesting and uses GRBL. I tried to find any info on the product but looks to be new and of course from China. I do like that the drivers are separate and heavy duty.
Yeah, that was reported as spam, but since it was on-topic and not obnoxious, I didn't act on it (and I think I closed the report).

FWIW, the RobotDigg folks got their start similarly and seem to be doing pretty well. Still debating about buying wider pulleys and belts from them, but trying to rationalize buying from a U.S. source in the hope that it'll be better quality.
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REdington
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Re: What are our current controller options?

Post by REdington » Tue Mar 31, 2015 4:46 pm

I'm using the Protoneer boards with Pololu 8825's and hopefully will finish the wiring today. I bought the assembled boards from

http://www.ebay.com/itm/171518581597?_t ... EBIDX%3AIT

Here is another place to get them as a package. I have bought from this seller and he is first class

http://www.ebay.com/itm/UNO-R3-NEW-ASSE ... 3a9eaf9f94

Another solution would use the Uno with a homemade shield with drivers and use esltcam, This limits you to estlcam though and it doesn't use GRBL on the arduino.

I'm not very computer smart, (took half a day to figure out how to load GRBL onto a UNO) but I do have 3 Pi 2's waiting for Windows 10 release for them. The plan is to use them on the 2 routers and the mill to run headless. Oddly enough, I ordered one of the CNC board's from PiBot to try on the mill with DQ542MA drivers that I have.

http://www.pibot.com/pibot-controller-board-rev2-0.html

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