Re: Problems with DAS-16

From: John Conner <conner_at_empiredi.com> · Date: Wed, 05 Jun 2002 08:20:52 -0600

I just checked with Measurement Computing and they confirmed that the 
CIO-DAS16JR 12 and 16 bit versions do not have FIFOs.  The manuals
do not list a FIFO in the specifications but the PC104 model does. 

I will try the cvs version.  Although it might be a day or so.  We have enough
of the PC104s to do the test so the priority has dropped a bit.  I also intend 
to put a scope on things and see what the real timing is.

John 

 > 
> Where did you get the info that the CIO-DAS16/jr doesn't have a fifo?
> Anyways, you might want to try the cvs version of the das16 driver.  It
> doesn't wait for the dma terminal count interrupt ( in order to work
> around buggy isa dma on some motherboards) and so is less likely to drop
> samples.
> 
> Frank
> 
> On Tue, 4 Jun 2002, John Conner wrote:
> 
> > Well I think I know why the CIO-DAS16JR is failing while the PC104-DAS16jr/16
> > works.
> >
> > The das16.c driver suggests a buffer size that will fill in 1/3 of a second -
> > given the values
> > I'm using this works out to 336 scans. Seems a bit familiar.  So the driver
> > has to process a
> > dma interrupt every third of a second.  The one thing I don't have is a number
> > for is how long
> > 1it takes to process the dma interrupt. My guess is something longer than 62
> > microseconds.
> >
> > There is one REALLY BIG but mostly undocumented difference between the
> > CIO-DAS16jr
> > and the PC104-DAS16jr/16.  The PC104 Board has a FIFO!  It does not have any
> > real
> > access the way most FIFOs do it just sets in the data path.  The FIFO is 512
> > samples deep.
> > The PC104-DAS16jr/12 also has the FIFO.
> >
> > What happens is that the boards continue generating samples while the DMA
> > system is being reset and some of the samples are dropped on the CIO board. On
> > the
> > PC104 board they stack up in the FIFO and are eventually read out.
> >
> > Looks like current comedi das16 driver will not work at the rates I need with
> > the CIO-DAS16jr
> > boards.
> >
> > John Conner
> > Empire Digital Instruments
> >
> >
> 
> 
> 
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