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Raspberry Pi, Arduino, Shield, GRBL, CNC, etc.

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Joules:
SD card reliability is usually down to quality, pay more get reliable cards.  We have high spec cards that are used for HD digital video and multi track audio recording.  The cards get heavy use and high transfer speeds.   These are the cards I use for low power computer use and not had a failure yet, plenty of trouble with cheap cards in our cameras and audio recording gear.

vtsteam:
Gerrit, still absorbing what you wrote.

It sounds like the Grbl "planner" is the look ahead function -- do you run a CNC machine that demonstrates to your satisfaction that it doesn't effectively slow down in doing multi segmented curves, and does outside corners reasonably sharply?

And it also sounds like I wouldn't need a shield since the alamode has pin outs to directly connect to drives like Gecko drives.

The final question is, whether the RPi is neccesssary --  it is running the GUI and a vnc server (or rdp, whatever). Your interface looks good, but I presume it runs only on a vbasic/Windows machine. Are there front ends for Grbl that run on a linux machine, and how would a notebook/desktop/tablet or whatever interface to the alamode, if there were no Pi? Or would you not have chosen the alamode in the first place?

gerritv:
This video shows my 'build enough to see if it will all work' machine at work cutting T6061. Feed rates are too slow, that was part of the subsequent adjustments. and

Grbl interprets Gcode just as Mach3 or LinuxCNC do. (but not as extensive a set of codes). So it corners as it is expected to. Grbl also pre-plans enough so that all but the very shortest segments run at full speed. A long sequence of short segments with my GUI will hesitate once in a while as I have not yet implemented the high speed stuffing protocol. Grbl gets its data at 115,000 baud and my GUI shows the fullness of the queue as usually full.

There are other GUI's out there, most of the useful ones are listed on the Grbl wiki. Most run nuder Linux. Some are better than others, some hang for weird reasons, some do things to the Gcode on the way to Grbl (and some don't make it clear what they modify) etc. None take a machining approach though, they are geared more to small routers etc.

Yes, mine presently only runs on Windows PC's but I expect to make some 'dumb it down for Mono' changes soon to let it run under Mono on Linux and OSx.

You wouldn't need a shield if you wire the Geckos directly. But you will still need to use a machine to control the RasPi ( which will control the Arduino running Grbl). In my mind 1 computer too many.

Gerrit
Gerrit

vtsteam:
Thanks Gerrit. I like your panel best of the ones I've seen so far. Very nice!

And reading even more, it seems that though the RPi project this thread started out with used an Alamode board to connect to the RPi in a neat header plug-in way.

But that method wasn't necessary. It could also be handled via USB from the RPi (or another computer -- a laptop, say) to an ordinary arduino Uno running Grbl. The Rpi (or laptop) would run the GUI that feeds the Arduino the G codes.

And also a second computer wasn't necessary with the RPi. If it had a keyboard and monitor and mouse, it could run standalone instead of headless.

So a system could simply consist of an RPi (w/K,V,M) and an Arduino connected by a USB cable.

If that is so, and you had on hand, commercial stepper drivers with opto-isolated inputs that needed only step and direction signals, and you had limit switches in place, could the Arduino board be direct wired to these inputs, or would you need an interface board (I guess you call them "shields" -- sorry I don't yet know all the arduino jargon)?

Like so?



It seems like the simplest and least expensive system for me would be going that route -- basically I'd just need an Arduino Uno to complete a system?

ps. though mono would work to port your GUI to an x86 Linux, I'm guessing it wouldn't be possible for an ARM proc Linux like the RPi  :(

gerritv:
Hi
You got it Pontiac, (a saying from the old days)  :beer:, factoring to its simplest level.

Mono will run on a RasPi: http://logicalgenetics.com/raspberry-pi-and-mono-hello-world/

My setup has wires directly from the UNO to a DB25 which then connects to a combo breakout/stepper driver board. The only issue is that the Motor On signal should be inverted in this scenario as its default state from the UNO is on! It blips the motor on power down because of that, not a pleasant surprise the first time it happens. This seems to be related to the way db25 breakout boards are designed.

I found the UNO that I packed for our winter trip, I guess I had better get that port finished soon :-)

Gerrit

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