For a different approach... Open source controller hardware with 
attached display.

Getting a stable real time environment are why ShopBotTools and 
FlashCutCNC both use
USB attached controllers.  This is where the sensors and motors are all 
attached.
Control happens in the USB attached computer, typically Windows running some
client software that gives a display similar to Axis.

Even the open source robotic LeafProject.org does something similar, 
using a PIC
or similar board to control wheels and sensors, and the 'main computer' 
is a Windows
laptop, in this case running a LISP interpreter.

The CarveWright.com machine does something similar but has a dedicated 
controller
and a SD card interface for loading programs.

We could consider a small 'off board controller'.  Hopefully opensource 
like the
Seguino control computer (A AMT micro processor that has a C like 
development
kit available for free).  This particular controller has quite a few 
both digital and analog
controls.  This might allow running EMC2 in a non-real-time 
environment.  I would still
like to keep it unix/Linux compatible even if someone wants to do a Mac 
or Windows
compatible port.

Historically I remember even IBM made boxes with high-speed (for the 
day) floating
point array processors where 'array programs and data' were loaded into 
these
I/O attached units then they processed independently, and send the data 
back when done,
and even 'attached CPUs' that had none of their own I/O but added raw 
processor
cycles.  Even the venerable Intel 286 and 386 chips had floating point 
co-processors that
were basically good calcularort chips attached.

I am not suggesting a g-code interpreter, but that might be OK on a 
larger unit, but possibly
a very simplified pseudo-g-code that could be used to implement a full 
g-code in conjunction
with the control/display computer.

Another option might be to get one of the 'single board' Linux machines, 
use it to run
EMC, and do AXIS on a 'display computer'.  This might make it easier to 
do the 'port' and still
keep the 'real EMC2' on hardware without display (or sound).  It could 
use either USB or
Ethernet attachment.

I could even see running Axis (or equivalent) on one of the little palm 
top computers, and EMC on
an 'attached controller box'.

Yes, there is some hand waving and daydreaming in this, but one day we 
need to start thinking this way.


Gene Heskett wrote:
> On Friday 21 November 2008, Roberto Caminiti wrote:
>   
>> Hi everybody,
>> I see that the newest hardware with frequency tuning and with many
>> advanced features not always give the best performances in terms of
>> latency, used with an RTOS.
>> So now I will ask you...
>> Are there on the market a special hardware designed to be used in
>> Real Time environment? Where?
>> So I think that this hardware is minimal, so I need only:
>> - VGA
>> - one or two PCI slot (for mesa cards)
>> - Serial ports and/or parallel ports
>> - One or two USB
>> - LAN
>> And so without advanced features like bluetooth, wi-fi, HDMI, audio, etc...
>>     
>
> The observations I can make are 1. onboard video is generally a bad thing for 
> realtime, particularly if it shares the mainboard memory.  It doesn't want to 
> give access back to the cpu unless threatened. 
>
> And 2. having a storage device, like a usb key or similar, plugged into a usb 
> port, also mungs the realtime stuff because of the device scans being 
> performed to see if its still there at frequent intervals.
>
> There may be others, one of which could be a mainboard std voltage of 3.3 
> volts rather than 5.  The 3.3 volt parport setups seem to be pretty picky 
> about who they talk to.
>
>   
>> Thank you!
>> Roberto
>>
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