<br><br><div class="gmail_quote">On Mon, Jun 7, 2010 at 7:29 PM, Eric Norum <span dir="ltr"><<a href="mailto:wenorum@lbl.gov">wenorum@lbl.gov</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div style="word-wrap:break-word">Indeed.<div>I suspect that many of us expressing concern about kHz and up system clock rates are showing our age --</div></div></blockquote><div><br></div><div>Hey, I resent that notion! I'm no where near as old as you :)</div>
<div><br></div><div>Or is denial just one of the symptoms of getting old ?</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div style="word-wrap:break-word">
<div> we used 50 Hz to 100 Hz system clocks back in the days of MVME167 cards (25 MHz 68040). Machines are a lot faster now -- perhaps a 5 kHz clock is not unreasonable nowadays.</div></div></blockquote><div><br></div>
<div>
For the record, I also use 1 kHz ticks on our MVME3100 (667 MHz) boards and on various x86 platforms (from 450 MHz to 3 GHz). No problems.</div><div><br></div><div>But, if one can utilize the time-base provided by a sampling ADC, that may be the right choice to drive this application.</div>
<div><br></div><div>Just a thought.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div style="word-wrap:break-word"><div><br></div><div><div><div>
</div>
<div class="h5"><br><div><div>On Jun 7, 2010, at 3:18 PM, Till Straumann wrote:</div><br><blockquote type="cite">
<div bgcolor="#ffffff" text="#000000">
Not sure. Having a higher resolution system clock can be quite useful<br>
since it allows you to use finer-grained timeouts (on semaphores,
queues, sockets, ...)<br>
or RTEMS timers etc. which can be desirable.<br>
<br>
I have started to use a 1kHz clock by default on our MVME6100 boards<br>
(1GHz powerpc) without noticeable impact on CPU load.<br>
<br>
-- Till<br>
<br>
<br>
On 06/07/2010 05:00 PM, Daron Chabot wrote:
<blockquote type="cite">Matt,
<div><br>
</div>
<div>I've used a 455 MHz Pentium 3 interrupting at over 20 kHz as
part of a VME-based data acquisition system.</div>
<div><br>
</div>
<div>I agree with Robert: if you can generate interrupts at the
frequency you need, _without_ using system's "ticks", that's the better
approach. Hopefully your ADC hardware can generate interrupts upon
conversion, or upon a "high-water-mark", or something similar...</div>
<div><br>
</div>
<div>If that's not an option, you may be able to use one of the spare
timers on the i8254 chip (if your system is so equipped).</div>
<div><br>
</div>
<div><br>
</div>
<div>-- dc<br>
<br>
<div class="gmail_quote">On Mon, Jun 7, 2010 at 4:23 PM, Robert
Deschambault <span dir="ltr"><<a href="mailto:robert.deschambault@gmail.com" target="_blank">robert.deschambault@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="border-left:1px solid rgb(204, 204, 204);margin:0pt 0pt 0pt 0.8ex;padding-left:1ex">Hi,<br>
<br>
In my opinion, I wouldn't run the RTEMS with a clock tick like that, I
would find a way to generate an external interrupt based on a hardware
timer. I have successfully run RTEMS on a 40 MHz LEON2, with no
changes to the RTEMS clock ticks, to accept a 16 KHz interrupt signal
for a fuzzy logic control loop to control a gimbal. Worked very well.
<div>
<div><br>
<br>
<div class="gmail_quote">On Mon, Jun 7, 2010 at 4:12 PM, Matt Rippa
<span dir="ltr"><<a href="mailto:mrippa@gemini.edu" target="_blank">mrippa@gemini.edu</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="border-left:1px solid rgb(204, 204, 204);margin:0pt 0pt 0pt 0.8ex;padding-left:1ex">Hi
-<br>
<br>
I would like to know your thoughts regarding common practices for an
RTEMS system requiring a 5 KHz sample rate. The hardware is 600MHz
i386/PC-104 based. Reading through the RTEMS C users guide the Rate
Monotonic Scheduler appears to be what I'm interested in. Basically I
need to read inputs from hardware, filter and process results, then
write outputs with a period of 200 us.<br>
<br>
I understand I can set the RTEMS system clock ticks to get this
resolution. My question is, is this a common and recommend practice for
this kind of sample rate? Or do people favor using on-board
programmable interrupt timers for this purpose? Is using an external
interrupt timer on the pci bus a common practice if your SBC doesn't
provide any timers?<br>
<br>
Thanks for any input.<br>
<font color="#888888"><br>
-Matt Rippa<br>
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</div>
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<br clear="all">
<br>
</div>
</div>
<font color="#888888">-- <br>
Bob Deschambault<br>
6614 Astro Court, Mississauga<br>
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cell: 416 457 7163<br>
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<pre><fieldset></fieldset>
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<span style="border-collapse:separate;color:rgb(0, 0, 0);font-family:Helvetica;font-size:medium;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><div>
-- <br>Eric Norum<br><a href="mailto:wenorum@lbl.gov" target="_blank">wenorum@lbl.gov</a></div></span>
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