>This is the only way to run what is known as 'hard real time' in this
environment.

>It may not be pretty, but it works.


Unfortunately the general Ubuntu users population doesn't need realtime 
response, so the real time kernal mods are an add on. Still it is hard 
to complain too much when you compare it with
the Microsoft situation. At least the Linux kernel is out in the open so 
it can be modified for realtime operation. No such luck with Microsoft. 
There are Windows add ons for realtime operation but they are also 
closed source and very pricey.

The problem with a smart SmoothStepper type device is that it cannot be 
altered by the general public (same as most other commercial CNC 
controls..).

The list of issues with the SmoothStepper is still fairly lengthy.  And 
due to economic issues, demand, the time limits of the developer, etc, 
the development cycle on the smoothstepper has slowed and perhaps 
stopped.    Many Mach3 users went to the Smoothstepper only to give up 
on it and go back to the Mach3 LPT driver since they lost 
functionality.  If you want to see an example of this in the Mach3 
world, go to the Mach3 forum and do a search on Threading....  there is 
a lot to read about that...  and the different ways that the 
Smoothstepper vs Mach3 handles threading has created some issues which 
are hard to overcome...    Then if you want to delve further look into 
rigid tapping...and why it is possible with EMC2 and not with Mach3..  etc..

The SmoothStepper was not able to implement all of the functions that 
Mach3 has.  As the EMC2 developers explained to me, that is why EMC2 is 
setup as it is.  The heart and soul of EMC2 is in software, alterable by 
multiple
people.  In most cases going to different I/O hardware (Mesa, Pico 
Systems, etc) does not cause you to lose core functionality.

The power of EMC2 is in the software architecture and that it is open 
source with many active developers.

Many EMC2 users are also quite familiar with Mach3.  ;-)

Dave



On 4/9/2010 9:14 PM, [email protected] wrote:
> I agree with Stephen.  The real time kernel is not an inherent part of
> what Ubuntu does.
>
> Basically it is a microkernel that drives the physical devices and
> runs Ubuntu, and its applications including the rest of EMC as a task.
>   If an interrupt happens, the microkernel
> takes over, when it is done it lets 'lower priority functions' like
> running Ubuntu do what it wants.
>
> This is the only way to run what is known as 'hard real time' in this
> environment.
>
> It may not be pretty, but it works.
>
> ...
>
> Other options are to offload all the real time functions to an
> appliance like Smooth Stepper by Warp 9 ( http://www.warp9td.com/ )
> but it isn't (yet) EMC friendly. (Smooth Stepper requires Mach3 and
> Windows to work sofar)
>
> For the 'old timers' that there are the DOS g-code interpreters.  They
> were effectively stand alone but used DOS as a program loader.
>
> I hope this helps someone...
>
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>    


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