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Design Question. Data Acquisition/Display related.

 
 
StepH
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      05-17-2005
Hi,

I'm building a little application, which the goal is to:

1./ Collect data via Serial line and or via a file (for playback).
2./ Display these data as graph, oscilloscope, ...

How manage this ?

1./ Is each "display" must responsible to acquire/read the data ?
2./ Or an engine collect the data then send them to each "display" ?

Also, how to "anim" this ?

1./ Via a timer ?
2./ Via a simple loop (read/update display/pause/read user key)

The app. will be a GUI (tkInter) app. and the user must be able to stop
the process at any time.

Sure, all this must be maintenable, let's say to acquire data via other
type of channel or to other type of display...

Yes, it's like a "mini" labView...

Any idea or link is welcome.

Thanks.

STepH.
 
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Alex Verstraeten
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      05-17-2005
StepH wrote:

>1./ Is each "display" must responsible to acquire/read the data ?
>2./ Or an engine collect the data then send them to each "display" ?
>
>
>

I'd keep it simple:

- DataCollector class
asociated with one or more display instances (implemented as a list of
display subscribers)
it collects data from a source and notifies each subscribed display that
new data is available.
could something like a 'collect' method which performs:

for display in self.subscribed_displays:
display.update( data )


- Display class
just a simple display class with an "update" method
it should be able to receive new data
and display new data
(those 2 actions could be implemented in different methods, you might
not want to display everytime new data is available... maybe you might
want to consolidate data in some way and output it at some high interval)

>Also, how to "anim" this ?
>
>1./ Via a timer ?
>2./ Via a simple loop (read/update display/pause/read user key)
>
>


a simple loop could do it
- handle user events
- collect data
- update displays
- sleep


 
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StepH
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      05-17-2005
Alex Verstraeten a écrit :

> StepH wrote:
>
>> 1./ Is each "display" must responsible to acquire/read the data ?
>> 2./ Or an engine collect the data then send them to each "display" ?
>>
>>
>>

> I'd keep it simple:
>
> - DataCollector class
> asociated with one or more display instances (implemented as a list of
> display subscribers)
> it collects data from a source and notifies each subscribed display
> that new data is available.
> could something like a 'collect' method which performs:
>
> for display in self.subscribed_displays:
> display.update( data )
>
>
> - Display class
> just a simple display class with an "update" method
> it should be able to receive new data
> and display new data
> (those 2 actions could be implemented in different methods, you might
> not want to display everytime new data is available... maybe you might
> want to consolidate data in some way and output it at some high interval)


Ok, it was my first idea too...

>
>> Also, how to "anim" this ?
>>
>> 1./ Via a timer ?
>> 2./ Via a simple loop (read/update display/pause/read user key)
>>
>>

>
> a simple loop could do it
> - handle user events
> - collect data
> - update displays
> - sleep
>
>
>

Here i've a prob. (due to the fact that I start both with Python &
TkInter). In TkInter, you run your app by launching a mainloop()
routine, right ? So, how, in my forever loop (handle user events /
Collect data / Update Display / Sleep) handle the user data ?

Sure, i can (i suppose), log user activity (via the event send by the Tk
underlayer), the "poll" theses event in my for ever loop ? But in this
case, are these event will be correctly generated (by Tk) ? How to
"give the hand" to Tk in such scenario ?

Thanks for your help.

StepH.
 
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Alex Verstraeten
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Posts: n/a
 
      05-17-2005
StepH wrote:

>>a simple loop could do it
>> - handle user events
>> - collect data
>> - update displays
>> - sleep
>>
>>

>Here i've a prob. (due to the fact that I start both with Python &
>TkInter). In TkInter, you run your app by launching a mainloop()
>routine, right ? So, how, in my forever loop (handle user events /
>Collect data / Update Display / Sleep) handle the user data ?
>
>Sure, i can (i suppose), log user activity (via the event send by the Tk
>underlayer), the "poll" theses event in my for ever loop ? But in this
>case, are these event will be correctly generated (by Tk) ? How to
>"give the hand" to Tk in such scenario ?
>
>Thanks for your help.
>
>StepH.
>
>

oops, sorry, I was thinking of a 'pygame' kind of loop, where you have
control over it.
I dont have experience on Tk, I allways use wxPython or pygame for gui's.

you can forget about the loop I mentioned... it doesn't apply to
event-driven applications where you have no control over the loop.
you'd be using a timer that triggers a tick method at a certain
interval, in that tick method you could tell your data collectors to
collect data... then the data collectors would trigger all its
subscribed displays's "update" function, so they draw the new available
data, just like the "for display in self.subscribed_displays:
display.update(data)".

so it comes to something like this:

tk mainloop is set to call tick() every 100ms through a timer.
tick() will iterate through all data collectors and call their "collect"
method
each data collector will then collect data and iterate through all
asociated displays calling their respective 'update' method on each.

of course there are plenty of ways to design an app, this is just an idea.

hope it helps,
Alex











 
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