Experimental Physics and
Industrial Control System

John Sinclair <[email protected]> · Mon, 10 Sep 2007 15:12:46 -0400

Emanuel,
One could imagine many systems with requirements which the use of a
real-time kernel could satisfy.

For example, suppose you needed to talk to some synchronous serial device

that required the generation of output signals at precise intervals of
precise duration and so forth.

If the device could tolerate +/- 50 us in the duration of this signal,
then you would need to

be sure you could change its state with the same time precision. You
could do this easily

with an FPGA or some other dedicated piece of hardware, but +/- 50 us is
also in the range of a

software solution running under VxWorks or RTEMS or even some RTlinux.
Running the software

on a non-realtime kernel would probably work most of the time but not
all of the time. Doing the

same using posix realtime scheduling would be better, but it would still
be possible for a piece of driver

code to cause problems so a realtime kernel (preemptive kernel using
realtime scheduling alone) would

be the only reliable software solution (assuming we are excluding a
hard-realtime solution).
John Sinclair
Emmanuel Mayssat wrote:

Hello,
I was wondering what would justify moving to RT linux?
I was actually contemplating doing the move to RT myself, but finally
decided against it.
All RT-required feedback/acquisition/etc are implemented in
hardware/electronics. As a result, my IOCs don't have to react
Real-Time.
But could you describe a "real" situation where RT is necessary?
Maybe if you have an IOC which is connected to a device that generate

hardware interrupts, etc. but so far I never encountered such a device.
Thanks,
--
E
On Mon, 2007-09-10 at 05:59 -0500, David Kline wrote:

you can use >=2.6.18 linux kernel/w patch from osadl
(http://www.osadl.org/). that will give you rt behavior.

/david
Heinrich du Toit wrote:

Hi
Did somebody else out there use RTLinux for EPICS?
-Heinrich

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System