On Thu, May 11, 2000 at 09:19:33AM -0700, Dan Samber wrote:
>
> I have a naive question:
> How does Labview benefit from RTLinux? Alledgedly, the people at National
> Instruments
> have arranged things (via special drivers or some other mechanism....) so
> that there
> are no ugly things like gaps in data acquisition etc.
>
> Can someone clear things up for me?
>
A good data acquisition board these days have hardware fifos that allow
them to sample at full speed (>100 kS/s) without dropping samples.
That being said, the operating system does have to guarantee _some_
maximum interrupt latency, in this case, at about 10 ms. Windows
can handle this until you walk away and get a cup of coffee. I've
never seen this failure under Linux (with my limited set of computers.)
PCI cards using DMA allow you to increase this latency indefinitely,
assuming you have enough RAM, and also assuming you have access
to the driver source code... =)
However, simple acquisition isn't very useful if your needs are more
complicated than streaming input and output. Very quickly, it becomes
necessary to record and generate synchronization events, accurate
timestamps, etc. These things can be done trivially using an RTOS,
but cannot be done accurately using LabView or any other user-space
tool. Using RTLinux is essentially like using NI's plug-in real-time
486 boards, except that you can use existing ISA/PCI-based hardware.
dave...
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For more information on Real-Time Linux see:
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