Re: Multi-axis sequenced move using asynMotor pseudo axis

["Pearson, Matthew R. via Tech-talk" <tech-talk@aps.anl.gov>]

Hi David,

The asyn motor driver functions are really designed to work within the scope of one controller. If all the axes were on one controller then I suppose it could be done within the axis::home() function, but then you’re turning a general purpose motor driver into an application specific driver. I’m not sure how it would work across multiple controllers, unless you created a new asyn driver that connected to each of the asyn ports for each controller, and a special homing function that dealt with the required logic. 

Using the database or SNL method would be a much easier approach. For the SNL approach you needn't have to have many states, just a ‘Idle’ and ‘Run’ state (and possibly an ‘Error’ state), with everything happening in the ‘Run’ state. Although, it would work better to have more states, such as ‘PreMove’ (that moves XYZ all in one go) and a ‘PostMove’ (moves XYZ back).

Cheers,
Matt


> On Mar 8, 2019, at 1:04 PM, David Vine via Tech-talk <tech-talk@aps.anl.gov> wrote:
> 
> Thanks Matthew and Kevin for your input, much appreciated.
> 
> I find the database implementation difficult to read and maintain. The SNL is more readable but there's a lot of boilerplate in setting up the states and connecting to PVs. 
> 
> Implementing the logic from within asynMotor has the following advantages:
> 	• readable and commented code,
> 	• the motor record has many of the PVs that I would need to connect to and monitor with SNL already,
> 	• i don't need to define states and all the overhead that goes with it because the axis::move and axis::home can implement all the logic
> I don't know if it makes sense but if asyn could implement an asynChannelAccessPort I think it would simplify this problem a lot. 
> 
> On Fri, Mar 8, 2019 at 8:28 AM Peterson, Kevin M. <kmpeters@anl.gov> wrote:
> David,
> 
> I find SNL programs to be cleaner than pure database implementations for 
> situations like this.  The SNL program might be more work initially, but 
> it is often easier to maintain, especially if the sequenced move 
> procedure needs to become more complicated in the future.  Breaking the 
> implementation into well-defined states makes it easier for others to 
> understand, troubleshoot, and modify the code.
> 
> Kevin
> 
> On 3/7/19 10:49 AM, David Vine via Tech-talk wrote:
> > Hi all,
> > 
> > I'm looking for the cleanest way to implement a sequence of moves of 
> > between different physical axes but hide it from the user so it appears 
> > as just a single pseudo motor axis.
> > 
> > For example, I want to home axis A but to avoid a collision I need to 
> > move axes XYZ to a particular location first, then home A, and then move 
> > XYZ back to their original position at the end of the homing procedure. 
> > And that sequence should occur just clicking the home PV of A.
> > 
> > I would like to set up a pseudo motor driver using an asynMotor driver 
> > and implement the logic there. Is it possible to do channel access calls 
> > from within an asynMotor driver? I couldn't find any examples. The 
> > physical axes are connected across three galil controllers.
> > 
> > Implementing the logic within an SNL program would work but it seemed 
> > simpler to do it within the motor driver.
> > 
> > Thanks,
> > David
> > -- 
> > Best regards,
> > David Vine
> > (925) 326 7503
> > dvine@sigray.com <mailto:dvine@sigray.com>
> > 
> > 5750 Imhoff Drive, Suite I  |  Concord, CA 94520  |  USA 
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> > 
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> > 
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> 
> 
> 
> -- 
> Best regards,
> David Vine
> (925) 326 7503
> dvine@sigray.com
> 
> 
> 5750 Imhoff Drive, Suite I  |  Concord, CA 94520  |  USA
> 
> http://www.Sigray.com
> 
>  
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