Lpc2000

Hi,

I'm new at this. Can someone tell me the best way to measure the time 
between external interrupt calls?
just point me in the right direction as to what to use..
thanks!

Jason

--- In lpc2000@yahoogroups.com, "jase_ko" <jase.ko@g...> wrote:
> Hi,
> 
> I'm new at this. Can someone tell me the best way to measure the 
time 
> between external interrupt calls?
> just point me in the right direction as to what to use..
> thanks!
> 
> Jason

anyone?.. how bout using a timer and increment a variable? or somehow 
tapping into an onboard clock?

At 04:36 AM 4/28/05 +0000, jase_ko wrote:
>I'm new at this. Can someone tell me the best way to measure the time
>between external interrupt calls?
>just point me in the right direction as to what to use..
>thanks!

It depends on what you are trying to do, your question is a little 
general.  Usually I just toggle an external pin and measure the result on a 
'scope.

Robert


" 'Freedom' has no meaning of itself.  There are always restrictions,   be 
they legal, genetic, or physical.  If you don't believe me, try to chew a 
radio signal. "  -- Kelvin Throop, III
http://www.aeolusdevelopment.com/

--- In lpc2000@yahoogroups.com, Robert Adsett <subscriptions@a...> 
wrote:
> At 04:36 AM 4/28/05 +0000, jase_ko wrote:
> >I'm new at this. Can someone tell me the best way to measure the 
time
> >between external interrupt calls?
> >just point me in the right direction as to what to use..
> >thanks!
> 
> It depends on what you are trying to do, your question is a little 
> general.  Usually I just toggle an external pin and measure the 
result on a 
> 'scope.
> 
> Robert
> 
> 
> " 'Freedom' has no meaning of itself.  There are always 
restrictions,   be 
> they legal, genetic, or physical.  If you don't believe me, try to 
chew a 
> radio signal. "  -- Kelvin Throop, III
> http://www.aeolusdevelopment.com/

well i have calls to an external interrupt method every time a pin 
is grounded.. This happens extremely quickly and i need an accurate 
way of measuring the time between the successive calls of this same 
method. I'm using an LPC2129

Thanks

At 09:47 PM 4/28/05 +0000, jase_ko wrote:
>--- In lpc2000@yahoogroups.com, Robert Adsett <subscriptions@a...>
>wrote:
> > At 04:36 AM 4/28/05 +0000, jase_ko wrote:
> > >I'm new at this. Can someone tell me the best way to measure the
>time
> > >between external interrupt calls?
> > >just point me in the right direction as to what to use..
> > >thanks!
> >
> > It depends on what you are trying to do, your question is a little
> > general.  Usually I just toggle an external pin and measure the
>result on a
> > 'scope.
>well i have calls to an external interrupt method every time a pin
>is grounded.. This happens extremely quickly and i need an accurate
>way of measuring the time between the successive calls of this same
>method. I'm using an LPC2129

In that case I'd definitely lean towards toggling an external pin.  That'll 
get you a number of useful pieces of information with two channels on a 
decent DSO.  Latency from pin going low to entering your procedure, length 
of your procedure, time between successive interrupts etc...  A decent DSO 
will have an envelope function and allow you to get a reasonable estimate 
of minimums and tell if you've missed any events.

Maximum information with minimal effort.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,   be 
they legal, genetic, or physical.  If you don't believe me, try to chew a 
radio signal. "  -- Kelvin Throop, III
http://www.aeolusdevelopment.com/

Hello Jase,

I would suggest to use a capture pin on timer 0 or timer 1 to capture 
the falling edge. This is more accurate because it eliminates the 
interrupt lattency.

Richard.


jase_ko wrote:

> --- In lpc2000@yahoogroups.com, Robert Adsett <subscriptions@a...>
> wrote:
> > At 04:36 AM 4/28/05 +0000, jase_ko wrote:
> > >I'm new at this. Can someone tell me the best way to measure the
> time
> > >between external interrupt calls?
> > >just point me in the right direction as to what to use..
> > >thanks!
> >
> > It depends on what you are trying to do, your question is a little
> > general.  Usually I just toggle an external pin and measure the
> result on a
> > 'scope.
> >
> > Robert
> >
> >
> > " 'Freedom' has no meaning of itself.  There are always
> restrictions,   be
> > they legal, genetic, or physical.  If you don't believe me, try to
> chew a
> > radio signal. "  -- Kelvin Throop, III
> > http://www.aeolusdevelopment.com/
>
> well i have calls to an external interrupt method every time a pin
> is grounded.. This happens extremely quickly and i need an accurate
> way of measuring the time between the successive calls of this same
> method. I'm using an LPC2129
>
> Thanks
>
>
>
>
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At 08:56 AM 4/29/05 +0200, Richard Duits wrote:
>Hello Jase,
>
>I would suggest to use a capture pin on timer 0 or timer 1 to capture
>the falling edge. This is more accurate because it eliminates the
>interrupt lattency.

Umm, how does

interrupt_occurred_at = timer_value;

have any less latency than

portset = 0x20;

??

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,   be 
they legal, genetic, or physical.  If you don't believe me, try to chew a 
radio signal. "  -- Kelvin Throop, III
http://www.aeolusdevelopment.com/

If you want to know when a falling or rising edge occurs the timer 
capture function copies to timer counter to the capture register when 
the edge is detected. If you use an interrupt to read the timer counter, 
you get the timer counter at the moment the timer counter is read and 
not the timer counter when the edge was detected. So when you read TC in 
the interrupt, the value is edge time + interrupt latency. If you read 
the capture register, it is always the edge time.

This works only for edge sensitive external interrupts and not for level 
sensitive or internal interrupts. You would also need to connect the 
external signal to a timer capture pin for this to work.


Richard.


Robert Adsett wrote:

> At 08:56 AM 4/29/05 +0200, Richard Duits wrote:
> >Hello Jase,
> >
> >I would suggest to use a capture pin on timer 0 or timer 1 to capture
> >the falling edge. This is more accurate because it eliminates the
> >interrupt lattency.
>
> Umm, how does
>
> interrupt_occurred_at = timer_value;
>
> have any less latency than
>
> portset = 0x20;
>
> ??
>
> Robert
>
> " 'Freedom' has no meaning of itself.  There are always 
> restrictions,   be
> they legal, genetic, or physical.  If you don't believe me, try to chew a
> radio signal. "  -- Kelvin Throop, III
> http://www.aeolusdevelopment.com/
>
>
> ------------------------------------------------------------------------
> *Yahoo! Groups Links*
>
>     * To visit your group on the web, go to:
>       http://groups.yahoo.com/group/lpc2000/
>        
>     * To unsubscribe from this group, send an email to:
>       lpc2000-unsubscribe@yahoogroups.com
>       <mailto:lpc2000-unsubscribe@yahoogroups.com?subject=Unsubscribe>
>        
>     * Your use of Yahoo! Groups is subject to the Yahoo! Terms of
>       Service <http://docs.yahoo.com/info/terms/>.
>
>

At 05:01 PM 4/29/05 +0200, Richard Duits wrote:
>If you want to know when a falling or rising edge occurs the timer
>capture function copies to timer counter to the capture register when
>the edge is detected. If you use an interrupt to read the timer counter,
>you get the timer counter at the moment the timer counter is read and
>not the timer counter when the edge was detected. So when you read TC in
>the interrupt, the value is edge time + interrupt latency. If you read
>the capture register, it is always the edge time.
>
>This works only for edge sensitive external interrupts and not for level
>sensitive or internal interrupts. You would also need to connect the
>external signal to a timer capture pin for this to work.
>
>
>Richard.
>
>
>Robert Adsett wrote:
>
> > At 08:56 AM 4/29/05 +0200, Richard Duits wrote:
> > >Hello Jase,
> > >
> > >I would suggest to use a capture pin on timer 0 or timer 1 to capture
> > >the falling edge. This is more accurate because it eliminates the
> > >interrupt lattency.
> >
> > Umm, how does
> >
> > interrupt_occurred_at = timer_value;
> >
> > have any less latency than
> >
> > portset = 0x20;
> >
> > ??

Methinks we are answering different questions.  That doesn't measure the 
interrupt response.  That measures the pulse.  Likewise toggling an 
external pin doesn't measure the pulse it measures the interrupt response.

I think the original question was how to measure the interrupt response 
characteristics.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,   be 
they legal, genetic, or physical.  If you don't believe me, try to chew a 
radio signal. "  -- Kelvin Throop, III
http://www.aeolusdevelopment.com/