Does Visa have any buffer/memory or similar?

[CarlosSp]

Yes, Ray caught it wright. I want that the LED turns on when data is refreshed and turns off instantantly, but it can be just in the next comparisson of the program that just gets a "false" because data has no changes. My concern is that what you say, that the LEDmay be turned ON always, but I don't think so because data refreshes every 1 or 2 seconds or less maybe, but not always I receive a good frame to refresh it, and at the beggining of turning ON all the stuff and while the GPS is gettins satellits etc, I don't have any data, so LEDS must be OFF until I start receiving it. 🙂 

[Ray.R]

So using the shift register should work for you.  Our concern was that the change would be so rapid that although the LED would be flickering, it would be so fast that the eye would perceive it as being either always ON or always OFF.

Do you need help to implement a shift register?

R

[CarlosSp]

Well, if the ON period is so short that human eye can't notice it, I would use a retard to turn it OFF.

I know the shift register but I'm not very familiarized with it. I know I need a while loop, but what should be the condition of that loop?

[Ray.R]

To stop a while loop you can have a stop button (simplest way).  You can OR the stop button with the status of the error cluster.  You can also OR it with whatever other boolean value that should stop the loop.

R

[CarlosSp]

Yeah but I don't want to be in a loop of lighting a LED all time, the application must run continoulsy and see if it's necessary to turn ON the led every loop of all the application, not beeing in a while loop all time 😛

[Ray.R]

In that case, you should already have a While Loop.  Simply use the While Loop that runs the application 🙂

[CarlosSp]

Ok, I implemented the solution that was only a feedback command and a not equal comparison, and works fine but as you expected, LED can't be seen ON because the lighting time is tooooo short, so I need something to keep it ON for a few time. By the time it's not necessary because I have not proved it with my whole application and maybe it works fine or maybe I will need that holding time, but not with a while loop that would slow my VI application.

[RavensFan]

Perhaps move the LED to its own little while loop.  Set up a notifier so that when the value changes, a notification is sent to this parallel while loop.