A routine that prints a small printk message and exits gets 100-150
interrupts per second which causes user space programs to halt. I'm
not sure if the interrupts would be faster without the printk
statemets. I'd hope not, since this is a 200MHz processor we're
talking about. ;)
At 08:01 AM 3/30/2005, you wrote:
Although Linux is not realtime,
you may still be able to do what you
want, depending on the latency required to *react* to the
pulses.
You can write an IRQ handler, which should be able to count pulses
accurately if there're not coming too quickly. I don't know what
the
lower bound (I.e. What is too quick) would be, so that's probably worth
investigating.
From there, your app can read from the IRQ driver how many pulses.
The
app is going to have latency, but you might not care about it
there.
--Andy Gryc
On Wed, 30 Mar 2005 11:54 am, zliminator wrote:
> Thanks for your reply. Too bad, I was kinda looking forward to
learning
> Linux. Now I'm wondering if there's any other OS that would work on
> this board that would be more suited to as an RTOS. Also, I seemed
to
> remember seeing a flavor of Linux that was supposed to be RT. I'll
have
> to do some research on google.
>
> Dan
> Ricardo Wiggers <> wrote:
>
>> zliminator escreveu:
>>> I want to use the TS-7200 for counting pulses from 1
or more
>>> hall-effect switches to determine wheel speed. I
also want to read a
>>> keypad, display results on an LCD and so on. I
remember trying this
>>> with either a 2800 (slow) or a 5300 from Technologic
using DOS/uCos
>>> and it seemed to bog down. I'm wondering if the 7200
running Linux
>>> will be fast enough without having to come up with
auxilary hardware
>>> like a PIC which reads the pulses and calculates the
wheel speed and
>>> sends the info to the 7200 in an sync serial format (a
lot of work and
>>> more to go wrong). Also, would Linux be the choice for
a realtime app
>>> like this? This is meant for a car and will probably
only read 2
>>> hall-eff switches to determine MPH and pulses from the
coil to
>>> determine RPM. The reason I'm reading 2 hall-eff
switches is to detect
>>> for wheel spin.
>>>
>>> Dan
>> Hi!
>> Linux is no realtime system. The RTAI port for TS7200 is going
on, but
>> is far from ready. Reading pulses is a trivial task for a PLD or
uC,
>> and
>> it seems a better option to count the pulses there and read it
and
>> process int the SBC, but you app seems to me (from the vague
>> description
>> above) more suited to be entirely done in a uC.
>> Ricardo
>
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