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Raspberry Pi | An ARM GNU/Linux box for $25. Take a byte!
Might be interesting for a cheap EMC2 video controller... 700mhz, 256mb ram, runs on an SD card. Not sure about USB support, but a port for smoothstepper would be awesome. Using an LPT port is probably out of the question.
Interesting idea, anyways. At $25 bucks it seems promising.
Writing drivers for the USB end might be interesting. I'd be worried about performance too considering the small ram size. Personally, I think implementing something on an android tablet would be a bit more feasible especially as far as product lifetime/lifecycle is concerned. Food for thought. :)
I would have thought it was better to control the CNC controller with the GPIO pins rather than any USB driver.
There is supposed to be a Gert-Board for expansion facilities on the Raspberry Pi. Not sure how many bits of the GPIO port is being made available in the first incarnation or how many EMC2 needs
The GPIO voltage levels are 3.3v so may need a chip like TXB0108 bi-directional level converter
Keith
That's interesting. I just posted about using this chip for a 3.3V to 5V fix for parallel ports and I did think to apply it to this situation. You can find the mention to it in my comment history somewhere.
As for the reason behind Android, it is a very widely used system and complete open source, so there are plenty of options for development. You would likely have to have the Droid talking to a secondary buffer board that holds lists of time-stamped future 'actions' and executes them according to realtime-clock ticks or a precision oscillator. This buffer-board could just implement a wireless protocall (say bluetooth) to talk to the Droid. Furthermore, the droid OS would allow for graphical control of the machine.
Sorry to disagree but I just don't see this happening for Andriod tablet. Because too difficult to interface hardware.
Also CNC needs real time operating system. There is one for Linux and not such a large step for Rasberry Pi which already is supported by various flavours of linux. EMC2 being the Linux implementaion on x86.
You are perfectly fine to disagree. You have a very good point.
Do you think Raspberry Pi and a SmoothStepper is the answer though? I can see it happening on the Pi, maybe with some extra hardware, but not with the SmoothStepper. It seems too... excessive.
Don't know much about Smoothstepper, but as far as I can see its a USB interface for Mach3 on a Windows PC. Unless they release the SDK for ARM & say Linux I don't see it as any relevance. I would have thought that USB is not the best way to go as there is a delay and lack of direct control. People used Printer ports on PC's because you have direct control of input and output pins. Trouble is what PC has a printer port these days. Given one is trying to drive CNC machines, I would always opt for Real Time Operating system ( i.e. Not windows ) and direct hardware interfacing. Both of which the Raspberry Pi should be able to do with the required developments.
I order my raspberry pi to play with. I also want to test if emc2 can work on it. The problem is I am not a linux guy. I will be more than happy if we can work on it together.
Regards,
Nuri Erginer
I am also interested in running am embedded RPi EMC2 system, I have some linux background and I am willing to help in any Raspberry Pi Project, I am waiting for a pi to come my way and am thinking about attaching some h-bridges to the gpio. its is all very early days still, but anyone else interested in the project PM me and I'll see if I can start putting some preliminary documentation / designs together. :cheers:
** Update ** Have just setup a project site. CNC Pi / Wiki / Home
I don't have much linux knowledge beyond being a user, but I will help wherever possible. It looks like it WILL have to use a smooth stepper, which is an extra cost, but considering the price of the Raspberry Pi it equals out quite nicely when you don't have to shell out a few hundred bucks for a PC. I doubt that a USB parallel port will work fast enough to satisfy the needs of EMC2, but if they could get it working it would be quite nice.
I think the biggest hurdle will be getting smoothstepper drivers to work properly within Linux.
Oddly enough an old machine works much much better. I gave up trying to use linuxcnc on a laptop, although an old Pentium 4 desktop works like a charm (I tried a Dell Dimension 3000 motherboard that I had on hand). These can be picked up for next to nothing these days, especially if you know anyone who is upgrading :).Quote:
Originally Posted by crane550
But I'd be interested in using a Pi as a controller source too!
Dynomotions k-flop works through USB. It also uses emc2 for g-code. It is a very powerful controller that takes the real time needs off the pc. It might make a good fit for what you are working on. I also don't see why you couldn't get it to work with an android tablet. Just my 2cents.
Judleroy
256Mb memory may be the limitation,
Mine's on backorder :(
Mini ITX isn't small enough ? :)
Linuxcnc adapted to this board sounds possible. Someone pointed out there is suitable I/O on board ? That would allow the pc (or whatever you call these things) to remain as a real time control and avoid USB. Linuxcnc is not restricted to parallel port afaik.
LinuxCNC does not support motion control through the USB port. It does support motion control through the parallel port, and through various other motion control cards like Mesa, Pico, I believe Galil, and some others. But not USB. There has been some talk of implementing it through real-time ethernet, but not as of yet.
Mark
is there a fundamental reason it doesnt support usb? or is it just cause noones done drivers yet?Quote:
Originally Posted by wendtmk
something to note about the raspberry pi is that it has no real time clock. i do not know myself if this is important to cnc control, but im guessing yes. you can add a clock on the gpio, but then you loose io which you really want to keep for control.
in any case, i really want to implement this little pc for cnc control, whether its linux or android or maybe even windows in the future.
Realtime Ethernet might be the answer. I think there could be potential for the Tablet option, but that warrants it's own topic. This is about the possibility for R. Pi as a low cost controller.
They've decided that the timing unreliability of USB in a real time situation was not worth the time and effort to create a path for a CNC control signal.Quote:
Originally Posted by ihavenofish
Mark
I would think an Android problem is simply that they have failed to fully adopt a single standard hardware port of any kind. Looks like many have "hacked" their way to all sorts of things with it.Quote:
Originally Posted by KeithSloan
Regarding "real time", there are dozens of CNC control programs that do not run "real time".... And, the many thousands of people using those controls don't let the terminology stop them from doing what they do, and do successfully. I suppose there is a "real time" argument to be had (and we have heard it plenty over the years), but it depends on exactly what a person happens to be controlling... exactly how "real time" any specific application >really< needs.
This raspberry looks not much unlike the small embedded PC's that have already been placed in OEM machines for years, pumping additional motion hardware... but clearly cheaper to purchase.
I say bring on the "black box". I've been using and heralding a black box product for years! It is a proven reliable and successful method. Its exactly where motion control started and exactly where it seems to be headed back to as PC component manufacturers slowly pull the plug on the parallel port.
the reason im asking is because we have a new 3 axis usb board from taiwan. they wrote mach 3 drivers for it and thus far, reliability seems a non issue (parallel port are NOT reliable in any way in my experience). so it may not be out of the question to ask them to write emc2 drivers that work with the raspberry (and other emc setups) if there isnt a fundamental road block. someone opinion that usb sucks for cnc isnt a roadblock to me.Quote:
Originally Posted by wendtmk
its a tiny board, not much bigger than the raspberry, and the 2 combined would make a seriously awesome all in one mini controller for well under $500.
:)