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<== Date ==> <== Thread ==>

Subject: RE: a puzzle about using stream device driver
From: "Mark Rivers" <[email protected]>
To: <[email protected]>, "tech-talk" <[email protected]>
Date: Mon, 20 Jun 2011 09:55:31 -0500
I don't think you can use I/O Intr, because the device only provides a
new value of the optical scale value when you ask for it.  If it sent
unsolicited updates of this value then you could use I/O Intr, but that
is not how most devices work.

Mark


-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Silver
Sent: Monday, June 20, 2011 9:42 AM
To: tech-talk
Subject: a puzzle about using stream device driver

hi, 

I am using stream device driver to communicate a galil motion control
which model is dmc21x3. To  get the value of optical scale, I use a ai
record like this:

record(ai,"$(PREFIX):opticalscale")
{
        field (DESC, "opticalscale position")
        field (DTYP, "stream")
        field (INP, "@dmc2143.proto ai_opticalscale motor")
        field (SCAN, ".5 second")
}
In that, I use the period scan. It works fine.
But in most of time, the value doesn't change. That means the IOC has to
communicate with device periodly. As the value only changes during the
motor moving,  may I use I/O Intr mode? 
I checked the online document of stream device, seems the I/O Intr mode
is not suitable for this case. Is there any good ways to avoid checking
the devcie periodly?
Thanks a lot for your help.

Best regards
Geyang  2011-06-20




References:
a puzzle about using stream device driver Silver

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