Re: [Daqpp-forum] scans

[Carlos L. <Car...@if...>]

Hello Andrej,

Yes, you can certainly use the vmedaq scans for that. However, as usual,
it will require some work on your side. The idea is that you create a
new runmanager and load it with the configuration file (via one of those
plugins) to be the one in charge of the scans. Say you create a run
manager that lives in the shared library libMyRunManager.so. Then in the
config file, in the plugins section you write

<plugins>
   <plugin> ...whatever you might already have.. </plugin>

   <!-- User defined run managers -->
   <run_managers>
      <scan>
         <lib>path_to_the_lib/libMyRunManager.so</lib>
         <hook>create_scan_run_manager</hook>
      </scan>
   </run_managers>

</plugins>

That means that in your library there should be a static "C" function
called create_scan_run_manager (it can be any valid name for a function)
that actually creates the run manager and returns a pointer to it.

Now, user defined RunManagers are defined like user defined modules but
are much easier, since you do not need to define GUIs, configurations
nor anything like that. Take a look at the example in  making_a_module.

To create your RunManager, I would propose to take ScanRunManager in the
daq folder and build from that. You will have to remove its
"relationship" with PulseRunManager, since you do not need that, and any
call to methods to that class. Yes... I know that should be a "generic"
class, and I promise I'll try to make it in the next release.

How the thing works...   All the sugar is in ScanRunManager::Trigger.
There it determines if we should start a new point in the scan or not
and notifies to the modules. I guess that if you just need to move axes,
the modules do not need to be notified, but who knows... This can be
done in 2 ways, either change every N events or change every N seconds.
Depending on the method, one uses an EventCtr instance or an EventTimer
instance. This is done automatically, so I guess you only need to edit
the files to remove the dependencies with PulseGenerator and, in
Trigger, move your stuff whenever  (*next_point)() is true.

Hope that helps. 

Regards,

Carlos

On Mon, 2007-02-19 at 11:54 -0500, Andrej Studen wrote:
> Hi Carlos, everyone!
> 
> I have a question. In what way is it possible to tamper with the scan
> modality of VMEDAQ?
> 
> Let me illustrate. What I have here is a scintillator camera which needs
> to be recallibrated from time to time. To do that, we use a XY table and
> record N=3000 events at a set of different positions (PMT centers,
> orthogonal grids, etc.). I am tempted to use VMEdaq to do that. But my
> user supplied scan routine should call external functions (move the motor,
> parse and analyze the data, move to next position) at each position. I
> think it fits nicely into a scan philosophy. So, my question is: can I do
> that and if I can, what guidelines should I follow.
> 
> A happy monday to everyone
> 
> Andrej
> 
> 
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-- 
 ___________________________________________________________________
 Carlos  Lacasta                        
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