Hi,
probably the following thoughts sound stupid to the experts
in this list, but anyway I will try to explain. For several
months I have been following this group, but still there are
some unresolved problems torturing my brain. Before I pose
some questions, however, let me explain what I would like
to implement on a 486/33 equipped with an Avantech PCL818
data aquisition board:
After starting an X application and setting some parameters,
the card is initialised to issue an interrupt at a defined
frequency (approximately 1-5kHz). Then the following should
happen until the measurement process is stopped by the user
application:
1. IRQN issued by card, interrupt handler called,
2. interrupt service routine calls functions like
- read some values from card into a fifo buffer
- output some values from a ring buffer
these functions are either implemented by a rt-module
or as driver functions.
The fifo buffer has a fixed length and can be read by the
user process entirely, the ring buffer is used in order
to output a periodic function which can be defined from
the user programm.
1. Would an ordinary linux kernel be sufficient or do I have
to use rt-linux in order to guarantee that this periodic task
can not be interrupted by any other interrupt?
2. Even though some drivers for several data aquisistion cards
are offered at the llp site, I wonder how people cope with
real time issues using these drivers. As far as I understand
rtl (thanks to Tomek), a conventional driver cannot be accessed
within a rt-module, unless this code is integrated in itself.
3. If the real time module controls the data aquisition
card entirely, how can I pass configuration information to
it from a user programm, like start conversion, set sampling
frequency etc.?
4. Is it reasonable to make an own module exporting some
hardware related functions e.g. rt_read_DAC0 for the
data aquisition board in addition to a real time module
(not necessarily a process) and the fifo module? Who will
register the interrupt of the board then? How will they
work together?
5. Is it even necessary to use rt_sched, if I had only one
periodic task? My common sense would say no. Insert just one
module in a real time kernel in order to not being interruptible
would do the job if timing is done by the card itself?
Lots of questions which to find a solution because I had
promised to my boss that a Linux real time application
will be ready soon and in addition be superior to a DOS98
based one.
Thanks in advance,
peterw
--
Dr. Peter Wurmsdobler
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Ceterum censeo MIRCOSOFTem esse delendam.
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