Rasberry Pi?

Guys got to ask this question and i know it is down the USB whatever route but it still can not be ignored. There seems to be an opportunity here to have a self contained unit with a small footprint. even if something else like a smooth stepper was required. What's the thoughts? is anything going to happen at some point to utilise usb?

PS

I do understand why it is not used now.

probably not ever going to see USB motion control product hooked to EMC.
see here for an idea why:
wiki.linuxcnc.org/cgi-bin/wiki.pl?Emc2HardwareDesign

Not that it is completely impossible. There are large (in linuxcnc developers opinion) trade offs.
Yishinli has made an linuxcnc based machine that used USB to communicate to a Mesa 7i43 card.
en.araisrobo.com/

In short USB sucks for realtime control. Which means the realtime control must be AFTER the USB connection (ie in the little black box)
which goes against the basic idea of Linuxcnc (PC based motion control).

Chris M

And it may be possible to port all of EMC to run on a Raspberry thus keeping EMCs
clean "all control in one place" architecture, and just use USB for appropriate peripherals
(storage, HMI etc)

Agree entirely and understood most of these points before posting, at the end of the day the usb port is designed for moving data no matter what without much control on speed. In an ideal world the raspberry would have a true timed data port but it dos not. You can see why some of the big boys go down the route of proprietary interface and control. It is a shame as it would be great to exploit this without the need for a true pc. The itx board goes a short way but still is full of bloat hardware that is just not required.

the Raspberry has 17 GPIO pins so should be able to do anything you can do on 1 parallel port (which is also 17 pins)

Its also has SPI (presumable stealing some of the GPIO pins) This allows some fairly high speed
real time connections to external peripherals

That's interesting? I'm still waiting for mine to turn up so will have to have a look at that when it arrives

elinux.org/Rpi_Low-level_peripherals

ok just a good look at the site just now as it has not been available and it could be possible? it would just take somebody better than me to do it?

All,

I'm a hardware engineer and have done some work with embedded linux. I was curious what the appeal is toward raspberry Pi instead of other single board PC's. I'm a fan of raspberry pi. I've got 2 on ordered. The reason I like raspberry pi is the embedded HD decoder. It's good for connecting to a TV. I'll be using mine to play movies, etc through xbmc.

Has anyone considered a different single board embedded box that has I/O?

For me it's about the small footprint this thing takes without all the extra rubbish that normally comes along with most PC's. It would be nice to stick it in a small controller box with the rest of the kit. With the following this thing has would mean a good LTS as well.

I can't agree more. I'm new to linuxCNC, but am a mechanical engineer with embedded linux experience. I've worked on a couple projects that used other single board computers. The benefits are low cost, low power, simple, small, etc.

I wonder what the target criteria is? I've read a bit on the USB to stepper controller discussion. I wonder if a single board computer that has built in pci ports might be a good solution. With the current generation of boards, you can get pretty fast processors, DDR3 memory, etc.

In an ideal world would a 1.2ghz processor be enough? How many pci ports?

Here is a good processor selection tool to get an idea of what's possible.

focus.ti.com/en/multimedia/flash/selection_tools/dsp/dsp.html