There is an option you need to uncheck when you edit the event. When you open the 
"Edit events handled..." look at the bottom of the dialog box and uncheck "Lock front 
panel until the event case for this event completes". Also, the event structure queues 
event changes, even if you might not want it to.



Subject: Event Structure locking front panel control
From: "E. Blasberg" <[EMAIL PROTECTED]>
Date: Thu, 10 Jun 2004 12:12:49 +0300

Hi All,

I discovered something unusual (at least to me) about the Event 
Structure in a State Machine which I don't entirely understand.  I've 
verified that it works the way I will describe below in both LabVIEW 
6.1 and 7.0 (under Windoze XP).

1) Make a Boolean on the front panel (NOT Latched)
2) Make a State Machine with the following states: Poll, 1, 2.
3) In Poll, make an Event Structure with no Timeout and only one 
event: Boolean Value Changed
4) If the Boolean changes, send the State Machine to state 1 (I put 
Wait 200 ms in States 1 & 2)
5) In State 1, if Boolean = True, stay in State 1.  If False, go to State 2

What I found is that I can get the code to go to State 2 just fine (I 
see it looping with the lamp on) when the Boolean is set to False. 
However after that, I cannot click on the Boolean on the front panel 
any more- it seems to be locked!  State 2 was supposed to send the 
state machine back to Poll when the Boolean went True, but there's 
just no way to click on the Boolean.

Emperically I guess this is the way it's supposed to be, but I don't 
understand why.  My guess is that the Event Structure is somehow 
trapping changes to the Boolean and then freezing it but, again, I 
have no idea why this should be.

I expect many of you will reply "Why in the world do you want to do 
this (especially since the above logic probably seems pointless)?" 
I'd prefer to put that question off for now.  Suffice it to say that 
I needed this functionality and the only way to make it work was to 
no longer have the Event Structure track changes to the Boolean (the 
original program would go to State 1 for 30 seconds, unless the 
boolean was hit again before the time was up, at which point it would 
go to State 2 until it was turned back on when it would go back to 
State 1 until the full 30 seconds was up).

So, to be slightly more concise: any idea why an Event Structure is 
locking a front panel control when the software is in a state in a 
State Machine in which it (the Event Structure) is not being called?

Much thanks in advance for any enlightenment on this...
E. Blasberg
iDAQ Solutions Ltd


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