Re: a puzzle about using stream device driver

[Dirk Zimoch <dirk.zimoch@psi.ch>]

Geyang,

You probably want to disable scanning completely when the motor is not 
moving, not just reduce the rate.
From the position-set record FLNK to a seq or similar that sets moving 
to 1. Your position-read record can use the 'field(SDIS, "$(P)moving")' 
and 'field(DISV, "0")' directly to process only when moving is 1. The 
same for all other records that should only poll when moving.
If the device can be asked for "done" use this information to set moving 
back to 0 and all polling stops. This record should as well poll only 
when moving. If the device cannot be asked for "done", use a calcout 
record to calculate "done" yourself.

"I/O Intr" only works if the device is sending status updates 
automatically while moving, without being polled.
Dirk


Davidsaver, Michael wrote:
> A simple way to get different scan rates based on a binary status.  I
> haven't checked that this example works, but I think it gives the basic
> idea.
>
> Record(bi, "$(P)moving") {
> }
>
> Record(fanout, "$(P)slow") {
>   Field(SDIS, "$(P)moving")
>   Field(DISV, "1")
>   Field(SCAN, "1 second")
>   Field(FLNK, "$(P):opticalscale")
> }
>
> Record(fanout, "$(P)fast") {
>   Field(SDIS, "$(P)moving")
>   Field(DISV, "0")
>   Field(SCAN, ".1 second")
>   Field(FLNK, "$(P):opticalscale")
> }
>
> Record(ai, "$(P):opticalscale") {
> }
>
> Behavior of SDIS and DISV is described here:
>
> http://www.aps.anl.gov/epics/wiki/index.php/RRM_3-14_dbCommon
>
>
> > -----Original Message-----
> > From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-
> > bounces@aps.anl.gov] On Behalf Of Silver
> > Sent: Monday, June 20, 2011 10:42 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