Experimental Physics and
Industrial Control System

<[email protected]> · Mon, 20 Jun 2011 14:53:22 +0000

Hi,

In the asyn motor drivers we dynamically adjust the polling rate for motor axes that are moving. For example, we may poll at 2Hz as standard, but as soon as an axis starts moving we start polling that axis at 10Hz or 20Hz. This means we're not polling everything at the fast rate all the time (which may saturate the comms link).

So you could do something similar with stream device, and adjust the record SCAN rate based on if a move command has just been sent. And then reduce it back down to a slow SCAN rate (or even Passive) after the move has finished.

Cheers,
Matthew

> -----Original Message-----
> From: [email protected] [mailto:tech-talk-
> [email protected]] On Behalf Of Silver
> Sent: 20 June 2011 15:42
> 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
> 

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System