Is any solution for a retriggable first call ?

[Kunsheng Chen]

Hi everyone,

I am doing labview with some logic stuffs.  I got stuck by exploting a retriggable first call.

Here is the big picture I can see:

 There is a for loop, inside which there is a while loop. The while loop contains a case structure,  the 'first call node'  is connected to the case structure to specify 'true' or 'false'.  

What I was expecting to do was refresh the 'first call node' in each iteration of the while loop, but it seems the 'first call node' is a global variable.

I don't know whether there is any other solution to do it, I am thinking of event, semaphore, but I am new to labview and has no idea wheather they would works. Also I am wondering if labview has mechanism like 'stored procedure' in database. 

Any idea is well appreciated. Acutally I found one link from Bob's retriggable first call but have no idea how it could works . http://labviewinsights.blogspot.com/2008/09/retriggerable-first-call.html.  it looks too complicated to me.

Thanks,

Kunsheng Chen

[LV_Pro · Accepted solution]

The "first call" is exactly that, the first time through that part of the code. You might consider, since this is in a loop, a shift register which is set to T when entering the loop, set to F with in that "first call case", then at whatever point you wanted to "reinitialize" set back to T for the next time through. This will give you sort of the first call effect, although if this loop is exited and re-entered (if it is in a VI that is called from a higher level) you will loose the "first call". Usually first call is used when in say an initialization routine, there are things that are only done once when a program is run, never to be done again until the program is stopped and restarted.

Message Edited by LV_Pro on 02-12-2009 10:41 AM