From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
To: Terry Fryar <terry.fryar@domain.hid>
Cc: xenomai@xenomai.org
Subject: Re: [Xenomai-help] Compile error
Date: Wed, 18 Jan 2012 23:32:28 +0100 [thread overview]
Message-ID: <4F17487C.8080508@domain.hid> (raw)
In-Reply-To: <E80344556EFF403586E4B8CAE727382F@TerryHP>
On 01/18/2012 10:44 PM, Terry Fryar wrote:
> I knew I wouldn't get enough...but I have other projects in between those
> timing requirements and I wanted to see how little latency I could get.
> Using an RTDM driver we wrote, I am measuring about 2us (not 20us) by
> triggering an irq off a gpio and pulsing another gpio line and measuring the
> difference between the irq edge and the pulsed edge using a logic analyzer.
That is probably because you are not measuring latency under load. So,
you do not see the worst case.
> I have a board that runs a suhdol linux sbc that is somehow handling gpio
> interactions within nanosecond ranges, and I have no idea how that is being
> done. Even flipping a gpio pin with direct register access inside a KLM is
> around 62ns. I just don't know how they are managing to detect a gpio pin
> state change and respond to several things all within a couple hundred ns??
>
> I've looked at their app files and it's just a gpio driver and what appears
> to be a single userspace app. A mystery I guess.....
I am talking about worst case here, not about average case.
--
Gilles.
prev parent reply other threads:[~2012-01-18 22:32 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-18 15:12 [Xenomai-help] Compile error Terry Fryar
2012-01-18 19:22 ` Gilles Chanteperdrix
2012-01-18 21:44 ` Terry Fryar
2012-01-18 22:32 ` Gilles Chanteperdrix [this message]
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