LabVIEW
New problem: How can I use DAQmx timing in the loop instead of "wait" vi?
Solved!
1). "Wait" is a node that doesn't return until the specified time has expired. In milliseconds. Fairly equivalent to, say "Sleep()" in Win32 threading models. A basic description is here: http://www.ni.com/white-paper/7592/en/ along with a counterpart that waits for a multiple increment of ms.
On the other hand DAQMX Timing vi configures the number of samples to acquire or generate and creates a buffer when needed.
The instances of this polymorphic VI correspond to the type of timing to use for the task.
The DAQmx Timing properties include all timing options included and additional timing options.
2). Can you be specific which LEDs are you referring to?
I really recommend you to use the built-in help, which will give you info about the different functions. See that small question mark at the top right of the front panel/ block diagram windows? If you turn it on, when you hover your mouse over certain functions, you get a brief description. Inside this Context Help window, usually you can also click on a "Detailed Help" link, which will open up a more detailed help doc!
Also, read through the DAQmx docs, like this: http://www.ni.com/product-documentation/2835/en/#toc3
(do not spend time with the DAQ Assistant, you can do everything with the low level functions you need).
Here I show a snippet which should get you started. Note, that you actual requirements should decide what kind of parameters you must use, like for sampling rate, samples per channel, line grouping, etc! Check the documentation how to use line grouping, and that Boolean 2D array should match with the DAQmx Write mode too (actually what are you trying to do with these Booleans? Can you detail your task?).
The usual way when you deal with DAQmx tasks is that, you initialize your Task, set up timing, start task, and now you enter only the While loop! It does not make sense and wrong way to reinit at every iteration! After the while loop stopped (due to an error or the user, see that Boolean OR function?), you can stop and clear the Task, then report any error if happened...
Hi leo,
2. When I click the button "STOP", there always will be LEDs turned on, what should I do to shut all the leds down when I click the STOP button?
Why do you create a new thread for the very same problem - you already got answers on that!
changing duty cycle of timing
Please explain that term!
And please STOP asking the same questions in several places! (I merged the threads…)
Hi leo,
The duty cycle means how much percentage between on and off when we put a "wait" button in a loop.
No, completely wrong expectation on your side!
The wait function will have the loop wait for (atleast) the amount of time you tell it to wait. What you do inside the loop in parallel to the wait function is up to you!
if we set 500ms as a constant for a "wait" vi, will there be only 250ms the led is on?(If so, the duty cycle is 50%.)
No! (Completely wrong expectation!)
To reach your goal you could set a wait of 250ms and switch the LED in each iteration…
A "wait ms" function does exactly what its name implies: it waits for a certain amount of ms. Nothing more, nothing less.
The code in the attachment will show you that when clicking the STOP button, there will always be a random led on. So I am just wondering how to turn all the leds off when pushing the STOP button.
As has been said before: you need to switch off the LEDs right after the loop.
THINK DATAFLOW!
