Ron wrote:
>
> I guess my first question would be, if your talking NTSC video at
> 60 fields per second i.e. normal 30 frames per second video, why
> are you bothering to use RTLinux in the first place, even an
> old 33mhz 486 can service interrupt rates that low (and do large
> amounts of processing in the interrupt service routine) without
> breaking a sweat. I've done it myself some years ago with a frame
> grabber I designed around the old philips SAA7195 chip set. Try
> doing what you need to do in userland, just as a test, I'll bet
> you'll see that 16ms is a very very long time on any newer
> processor.
>
> Loren Frank wrote:
> >
> > Hi all. I am new to rtlinux and I have a problem I need help with.
> >
> > Briefly, I need to take the bttv driver for a framegrabber card and modify it
> > so that, every time an interrupt is generated, the interrupt service routine is
> > serviced by the real time kernel and a timestamp is read from another card. I
> > have the real time driver for the other card working, but when I tried to
> > convert the interrupt service routine from the bttv-driver.c source, I just
> > ended up hanging the machine. I had hoped that a simple modification where I
> > changed the request_irq to a rtl_request_irq and changed the interrupt service
> > routine would do it....
> >
> > Can anyone point me toward a solution?
>
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We use Matrox video cards which have a standard Linux driver. I modified
the driver slightly so that whenever a frame is ready a task in the RT
area is called. In this way I close a telescope acquisition servo at the
nominal 30Hz frame rate. As Ron says, the user space driver can easily
handle the full frame rate, it was just convenient to link it with
Rt-Linux as I already had so much code for the telescope drive running
under Rt.
Theo
--
Dr. Theo ten Brummelaar
The CHARA Array-Georgia State University-Mount Wilson Observatory
http://www.chara.gsu.edu/~theo Ph: 626-796-5405 Fax: 626-796-6717
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