ticksize and timer_create()

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stefan

ticksize and timer_create()

Post by stefan » Tue Nov 05, 2002 8:51 pm

Hi....

i have the follow problem:

my requirements:
- x86 computer 400 MHz
- QNX 6.2 (momentics)

now, i change the ticksize from 1 milli to 0.01 milli., the smallest
ticksize, and i
have create a timer for impulse. so the timer should be give one impulse
per
0,01 milli seconds.
my problem is, when i use this timer my computer crashed very often!!!
is reason for this problem that the ticksize is to small or the timerimpulse
is to small??
when i change the timer interval to 20 micro or 30 micro the computer
crashed!

my target is, to trigger a muliti I/O-card in realtime with the impulse
from the timer!!

where is the problem?

can someone help me???

thanks :)

S. Kehrein

Adam Mallory

Re: ticksize and timer_create()

Post by Adam Mallory » Tue Nov 05, 2002 9:46 pm

I don't think your hardware/cpu could make much in the way of forward
progress if you have such a small ticksize. When you say "crashed" do you
mean you saw a procnto dump on the console, or that processes stopped
running (ie. made no forward progress).

Can you also explain what you're trying to acomplish with the I/O card as
it's not clear (at least to me).

-Adam

stefan <stefankehrein@lycos.de> wrote in message
news:aq9aim$3re$1@inn.qnx.com...
Hi....

i have the follow problem:

my requirements:
- x86 computer 400 MHz
- QNX 6.2 (momentics)

now, i change the ticksize from 1 milli to 0.01 milli., the smallest
ticksize, and i
have create a timer for impulse. so the timer should be give one impulse
per
0,01 milli seconds.
my problem is, when i use this timer my computer crashed very often!!!
is reason for this problem that the ticksize is to small or the
timerimpulse
is to small??
when i change the timer interval to 20 micro or 30 micro the computer
crashed!

my target is, to trigger a muliti I/O-card in realtime with the impulse
from the timer!!

where is the problem?

can someone help me???

thanks :)

S. Kehrein

Rennie Allen

Re: ticksize and timer_create()

Post by Rennie Allen » Wed Nov 06, 2002 8:20 am

2. the impulse is for my multi I/O card. this impulse is the sample rate. i
wish a sample rate from 50KHz,
that is the reason for the small ticksize.
the other reason is, the timer must be give a realtime impulse.
I've done 10Khz sampling on a 450Mhz computer running QNX4.2
using synthetic timers (i.e. proxies). 50Khz, doesn't sound
possible on your hardware. On a 3Ghz Pentium IV with synthetic
timers maybe; with a timer card generating interrupts certainly.

Personally it boggles my mind that one could use a general
purpose computer running an OTS OS with synthetic timers, to
sample an audio signal at CD quality, but on the very newest
machines it is possible (perhaps there'll be software only
audio cards soon; winaudio ? - so Dell can cut another
$10.00 off their price ;-).

Rennie

Adam Mallory

Re: ticksize and timer_create()

Post by Adam Mallory » Wed Nov 06, 2002 1:56 pm

I've posted the email sent privately, so all could comment. Stefan, please
keep newsgroup discussions in the newsgroup so all can benefit from shared
knowledge.

-Adam
-------------------

hallo,

at first thank you for your answer.

1. i need a very small ticksize for my impulse-timer. when i need a impulse
every 10 mico seconds
than i need a ticksize from 10 micro seconds at least. or ist that
wrong?
or gives an onther way to realize a small impulse?

2. the impulse is for my multi I/O card. this impulse is the sample rate. i
wish a sample rate from 50KHz,
that is the reason for the small ticksize.
the other reason is, the timer must be give a realtime impulse.

3. also, when my computer crashed then break down the complete system. the
screen is frozen.


thank you for your interest!

s. kehrein

Adam Mallory <amallory@qnx.com> wrote in message
news:aq9dnl$g1l$1@nntp.qnx.com...
I don't think your hardware/cpu could make much in the way of forward
progress if you have such a small ticksize. When you say "crashed" do you
mean you saw a procnto dump on the console, or that processes stopped
running (ie. made no forward progress).

Can you also explain what you're trying to acomplish with the I/O card as
it's not clear (at least to me).

-Adam

stefan <stefankehrein@lycos.de> wrote in message
news:aq9aim$3re$1@inn.qnx.com...
Hi....

i have the follow problem:

my requirements:
- x86 computer 400 MHz
- QNX 6.2 (momentics)

now, i change the ticksize from 1 milli to 0.01 milli., the smallest
ticksize, and i
have create a timer for impulse. so the timer should be give one
impulse
per
0,01 milli seconds.
my problem is, when i use this timer my computer crashed very often!!!
is reason for this problem that the ticksize is to small or the
timerimpulse
is to small??
when i change the timer interval to 20 micro or 30 micro the computer
crashed!

my target is, to trigger a muliti I/O-card in realtime with the impulse
from the timer!!

where is the problem?

can someone help me???

thanks :)

S. Kehrein



Andrew Thomas

Re: ticksize and timer_create()

Post by Andrew Thomas » Tue Nov 12, 2002 8:20 pm

2. the impulse is for my multi I/O card. this impulse is the sample rate.
i
wish a sample rate from 50KHz,
that is the reason for the small ticksize.
the other reason is, the timer must be give a realtime impulse.
Are you reading at 50KHz, or are you sending output at that rate
as well? Does your card have an on-board buffer? In my (limited)
experience, cards that sample at that rate also provide a way to
buffer multiple samples on-board so that the computer can read at
more realistic rates. Also, a board with that sample freqeuency is
likely to be able to generate an interrupt. If it does, consider using the
interrupt instead of a timer to collect your data.

I have no doubt that you will never get a reliable 10us timer running
without using a hardware interrupt. I suspect that if you are only
reading from the I/O card that there is a way to slow down your
program's read rate while maintaining the card's sample rate.

Cheers,
Andrew

"stefan" <stefankehrein@lycos.de> wrote in message
news:aq9aim$3re$1@inn.qnx.com...
Hi....

i have the follow problem:

my requirements:
- x86 computer 400 MHz
- QNX 6.2 (momentics)

now, i change the ticksize from 1 milli to 0.01 milli., the smallest
ticksize, and i
have create a timer for impulse. so the timer should be give one impulse
per
0,01 milli seconds.
my problem is, when i use this timer my computer crashed very often!!!
is reason for this problem that the ticksize is to small or the
timerimpulse
is to small??
when i change the timer interval to 20 micro or 30 micro the computer
crashed!

my target is, to trigger a muliti I/O-card in realtime with the impulse
from the timer!!

where is the problem?

can someone help me???

thanks :)

S. Kehrein

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