The Shop > Electronics & IC Programing
Raspberry Pi, Arduino, Shield, GRBL, CNC, etc.
vtsteam:
I just received a Raspberry Pi B+ for Christmas unexpectedly, and I'm trying to figure out what to do with it.
I was thinking maybe CNC, and came across this artcle on combining it with an Arduino and CNC shield, but I'm still left wondering why?
http://www.instructables.com/id/Raspberry-Pi-Alamode-CNC-Controller
It seems to me you're just left with a device that can accept G-code files and then push stepper motors.
But what gives you the graphic DRO feedback and operational controls (jogging, etc), like say, LinuxCNC or Mach 3, (or even TurboCNC) running on an old spare computer feeding stepper drivers though a parallel printer break-out board?
Do you still run, say, LinuxCNC on a computer concurrently with these other boards?
And once a G-code program is sent to the Raspberry Pi how do you interrupt, modify it? Is there some graphic CNC program running on it?
vtsteam:
A little more reading seems to be answering some questions -- Grbl seems to include a graphical interface and jog controls, and seems to run on the Rspberry Pi.
In the hardware project linked above, it looks like an additional computer(laptop) is used for an actual physical display for the headless Raspberry Pi through VNC via a (wireless) network. But the Pi is running the GRBL program, not the laptop.
In the project, an Alamode board hooked to the Pi provides a Real Time Clock and does the G-code to motion translation (I think). Finally a CNC Shield board seems to provide stepper drivers.
My questions now are,
1.) if I already have drivers, can I eliminate the shield board?
2.) Does GRBL provide look ahead buffer capabilities for motion control -- how square would corners be if this system was running a mill, and does the feed rate slow down from a straight line on doing arcs an circles made of polylines?
Brass_Machine:
Hi Steve,
Can't answer any of your questions about using the Arduino/Raspberry Pi for CNC. I do have an Arduino I got for fooling around with. Figured I needed to learn this stuff someday. But I do plan on getting a Rasp Pi very soon to do a car audio implementation.
Back to the CNC bit for the Rasp Pi. Would be curious to see how you get on with it. I have a laptop now for my controller. Though I do have an old PC waiting to go into the shop for my mill. Mind you, I am going to completely rebuild it... so this may be an alternative to the bulky pc.
Eric
vtsteam:
Eric, I'm writing this from the Raspberry Pi on our TV via HDMI. Boy that makes a big monitor! I'm used to a laptop and this is a 32" screen. Resolution is amazing via HDMI. Not quite the same league as the old TRS-80 days when you hooked up to your TV via an RF converter and got a fuzzy 16 x 64 characters! Yet this thing is the size of a pack of playing cards, and cost about $30.
I'm running Raspbian, a version of Debian Linux specifically tailored for the Raspberry Pi (mine is a B+ model). There aren't many applications that come bundled with it, and I have some favorites so I first installed Synaptic (an application program downloader that works with the Debian repositories), and with that installed Iceape (Seamonkey/Mozilla browser suite), Libre Office Suite, MtPaint, GIMP, and Libre CAD. I also added NoScript to Seamonkey to block web script junk, and deleted Google as the search engine and replaced it with Ixquick.
For getting started with these little boards, you need a fast SD card (micro for the B+ model) of 8 gigs or more ( I bought a 10x speed 16 gig -- $13) and this is actually essential, since the OS goes here, and must be downloaded separately (used my laptop) or the board won't boot.
You also need a video cable, a USB keyboard and mouse (can be IR with a dongle -- mine is). I happened to have an old USB wireless dongle also, and that worked out of the box to connect to my network. There's also an ethernet port on the board for a hard wired network connection. I had all the stuff I needed on hand already, except for the video cable and SD card, so it was all pretty easy. Oh yes, a 5V USB type power supply of 1 amp or greater capacity to help power the USB ports as well as the board ( I have a 2A supply).
Unfortuntately, from my reading, WINE won't work on the Raspberry Pi to run Windows programs on a linux platform, as it will on my notebook computer. This is beacuse the RPi has an ARM v6 processor, which has a different instruction set than the typical Intel x86 Windows machine. So both WINE and the applications would have to be re-compiled (or run on an emulated processor) -- neither of those are mean feats, and the performance hit would be substantial, probably. Thus I can't run Sketchup (CAD) -- the only reason I have to run a Windows program. But a very important one for me in a work computer.
But of course this isn't a work computer, really, and for everything else I can think of re. productivity or entertainment it would actually be fine! Which is remarkable for a $30 device. The screen is really beautiful -- easy on the eyes with a big monitor at high resolution. With 4 USB ports on board you could add a portable terrabyte drive, or a bluray drive or both. If you hook a powered USB hub, it would supply power to both the board and additional USB ports -- if you needed them.
I think this might just end up being a family computer in the living room! Well if it doesn't end up in a dedicated CNC box!. Heck, we could get another one for $30 and do both!
Well I am very impressed -- it's a lot better than I expected -- everything just worked great on installation, and the graphics are excellent. This is designed as an educational computer, but it isn't just for kids. It's a pretty decent desktop computer, to be honest.
Okay, back to the CNC topic:
Probably I'll next download a VNC server. This will allow another computer to view the RPi's desktop and run mouse and keyboard. In other words, allow it to run headless. This is what the setup referenced in the first post uses. The RPi thus doesn't need a keyboard, mouse, or screen -- it is operated by a remote computer (or tablet) running a VNC client, over the network.
So the next stage would be testing the VNC capability. I don't anticipate problems, since I've done this before.
mattinker:
That was fast!
Regards, Matthew.
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