5KHz acquisition control

Daron Chabot daron.chabot at gmail.com
Mon Jun 7 22:00:01 UTC 2010


I've used a 455 MHz Pentium 3 interrupting at over 20 kHz as part of a
VME-based data acquisition system.

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...

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).

-- dc

On Mon, Jun 7, 2010 at 4:23 PM, Robert Deschambault <
robert.deschambault at gmail.com> wrote:

> Hi,
> 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.
> On Mon, Jun 7, 2010 at 4:12 PM, Matt Rippa <mrippa at gemini.edu> wrote:
>> Hi -
>> 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.
>> 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?
>> Thanks for any input.
>> -Matt Rippa
>> _______________________________________________
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>> rtems-users at rtems.org
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> --
> Bob Deschambault
> 6614 Astro Court, Mississauga
> Ontario, Canada L5N 7J2
> home: 905 824 7159
> cell: 416 457 7163
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