On 31 May 2012 17:20, Dave <[email protected]> wrote:

> If you never under run the buffer you are ok, if you do, they fault out.
>   That's how they can run with a non-realtime system like Windows.
> They just spool up a second or more of move data, and then go to work.

Yes, but this would be very difficult with LinuxCNC.

If the original device can be persuaded to trust that the next axis
position will be along in 1mS, guaranteed, and not to fret about an
empty buffer then I can see it being relatively easy, as it can be
driven with a HAL component and RTNet. Otherwise it needs to slot into
the LinuxCNC system somewhere where no other hardware does.
If you look at:
http://git.linuxcnc.org/gitweb?p=linuxcnc.git;a=blob;f=src/hal/drivers/mesa-hostmot2/stepgen.c;h=0538d8a833be8d9f16a10d401f2934a5f01d5f6f;hb=0cd2f98d522b87d08f302260ceb571a6b4b46010
for example, that is the driver for the Mesa Hostmto2 cards, and it
basically sends a new step-rate command every servo-thread.
(the step rate required is calculated from the new position request,
the stepgen scale and the current position)

-- 
atp
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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