>>> [EMAIL PROTECTED] 29-10-01 15:25 >>>
On Fri, 26 Oct 2001, Der Herr Hofrat wrote:
> > Dear people of RTL-mailing list,
> >
> > We at NBG-Industrial (Location Nederweert, Netherlands) are trying to sample/count
>a TTL-signal with a frequency of 200 kHz
> > (or as high as posssible). We use a PIO-24 card (ISA-based) to generate an
>interrupt at
> > each pulse. The interrupthandler in RTlinux is used to increase a counter. In a
>seperate
> > thread, which starts up every second, the time is measured and the frequency is
>calculated.
> > The precision of the frequency was measured while linux itself was heavily loaded
>(compiling
> > a kernel). 20 kHz is the highest frequency which can be measured without a
>deviation. 25 kHz
> > is still measured reasonably well(a deviation of -6 Hz once in the 200 times). But
>frequencies
> > above 30 kHz are measured with a deviation of minimal 10 Hz almost every
>measurement (which
> > is too large). Is there a way too improve this performance? For instance
>optimizing core.c/core.o?
> >
> you could use an SMP box and run the data-sampling process on the dedicated CPU
> 200KHz is posible with this setup - you can run a 200KHz task on a Celeron 400
> SMP - but I don't know if you will be happy with the jitter. Also moving to
> a PCI card could improve things.
I am not as low-level as I'd like to be with respect to intel hardware
(yet!) but I was wondering what the real bottleneck is in this situation.
It's surprising to see that really you can't get an ISA device to
interrupt the CPU reliably over 20,000 times/sec. Would you mind walking
through the life of one little interrupt coming from the PIO-24 card in
this scenario?
Hello,
I was wondering the same. Maybe the problem is not only software but also (or mainly)
hardware. So I am going to focus on response time after one interrupt.
Greetings,
Erwin Triepels
>
> hofrat
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