RTLinux based project

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hi,
I'm new to this group and i really need a small help from u guys. I m
presently doing a course in embedded system design and we have a
project here in our curriculam of 1 month duration. i want to do the
project in RTOS(RTLinux specifically) but i m not able to figure out a
good idea. If any one has an idea about a good project (RTLinux based)
then i request to help me by presenting it to me...even let me know
about the various links on the internet about the same.

thanx in advance

Ravs


Re: RTLinux based project
Very simple project: create a PWM waveform on a bit I/O port, that is
fed to an RC network to create a steady voltage. If the system does not
support hard realtime the voltage will not be steady.

-Michael

Re: RTLinux based project
thanx michael, but can u present me few more detalis. How do i generate
the PWM and how do i measure the voltage. I have a fully furnished lab
and i m comfortable with AVR atmega16 microcontroller. based on your
idea what i figured out is that i can generate a PWM waveform from the
timer/counter 0 of the AVR ucontroller and can attain steady voltage
with an RC network but i m unable to get how can i program in RTLinux
for verifying the steadyness of the voltage.

thanx
Ravs

Michael Schnell wrote:
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Re: RTLinux based project

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Linux has nothing to do with verifying the voltage.  What he was saying
was that the RT routines will guarantee that the PWM widths are consistent
and timely within the precision of the system's hardware.  It is the
consistency of pulse widths and stable frequency that makes for a steady
mean average voltage output.

Verfication of the output voltage will need to be done externally, like
with an O-scope.



Re: RTLinux based project
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Use a bit I/O (printer port with a standard PC) and toggle one of the
bits (cyclically: x Ásec low, y Ásec high)

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using an oscilloscope.

I have a fully furnished lab
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I'm not :(.

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If you want to test/prove the realtime awareness of the system
(including software) in Linux, user land software should be involved in
the timing. So you e.g. would do use a fast running continuous timer
that blocks some resource. A user land process would wait on the
resource and when activated m (for high) or n (for low) times, it would
toggle the output bit.

Supposedly designing the software and deciding which kind of resource to
use is _your_ homework.

When I did a similar test some years ago (with Kernel 2.4) I found that
there were delays up to several 100 msec when using the IDE driver, even
though the timing measurement process was given realtime (shed-fifo)
priority. 2.6 is supposed to work a lot better and you can activate
kernel preemption to improve realtime behavior. But to do decent
realtime you will need more appropriate stuff (maybe RTLinux, which I
did not test).

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The software is just to create the PWM waveform. The result is measured
by external hardware (Oscilloscope, DC-voltmeter (is the needle steady),
AC-voltmeter (measuring the noise), loudspeaker, ...)

-Michael

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