topic Re: Input and Output State in LabVIEW

Input and Output State

Chris9823Alb — Wed, 10 Jan 2024 18:36:02 GMT

I have a doubt about LABview when I stop the program the I/O state still same before I click on stop program run , example I'm controling a servo motor and if I stop the program the servo still spinning , I just want how can reset the I/O status when I press to end the DAQ programm

Re: Input and Output State

Gregory — Wed, 10 Jan 2024 18:48:55 GMT

Hi Chris, you will have to share your code for specific suggestions. You can set the state of your DAQ card to whatever you need it to be (example set some outputs to 0 V) as your program is shutting down.

Make sure you are not using the abort button (stop sign next to run button) because that is only for emergencies. Your VI should complete its run gracefully e.g. when its task is finished, when a front panel control is pushed, or other stop event is triggered.

Re: Input and Output State

santo_13 — Thu, 11 Jan 2024 00:38:19 GMT

@Chris9823Alb wrote:

I have a doubt about LABview when I stop the program the I/O state still same before I click on stop program run , example I'm controling a servo motor and if I stop the program the servo still spinning , I just want how can reset the I/O status when I press to end the DAQ programm

Just to clarify, LabVIEW is a graphical programming language; the code you implement using LabVIEW, called "Application," is the one that interacts with your hardware. So, in essence, it would be more appropriate to ask how to achieve a proper shutdown on application close.

Your program must implement a method to properly power down or stop your external hardware, or else it will be like crashing a car into a tree to stop it; of course, there is the best way, to apply brakes, and again, not in the middle of the highway.

Re: Input and Output State

Chris9823Alb — Thu, 11 Jan 2024 12:16:42 GMT

This is my code , when I click to abort execution or program occur an error the state of I/O ports still same so the motor keep running

Re: Input and Output State

GerdW — Thu, 11 Jan 2024 12:31:02 GMT

Hi Chris,

@Chris9823Alb wrote:

This is my code , when I click to abort execution or program occur an error the state of I/O ports still same so the motor keep running

I don't see any "abort execution" button, I just see a "Stop" button. How do you "abort execution"?
I don't see any error handling in your VI: how do you react on "occuring errors"?
I don't see any code to gracefully shutdown your hardware system: where do you plan to place this code? (As has been suggested before!)

Re: Input and Output State

Chris9823Alb — Thu, 11 Jan 2024 14:14:24 GMT

I mean this button near pause , and how can I make my outputs restart when occur error or press this button?

Re: Input and Output State

crossrulz — Thu, 11 Jan 2024 14:57:15 GMT

@Chris9823Alb wrote:

I mean this button near pause , and how can I make my outputs restart when occur error or press this button?

Do NOT use that button. It is only meant as a last-ditch option when things go totally wrong. It is commonly compared to using a tree to stop your car. You cannot do any clean up when you abort the VI. Everything just instantly stops where it was. This is catastrophic when dealing with hardware.

You need to use your actual stop button on your front panel to gracefully let the loop stop, then set your outputs to "off", and then stopping the DAQmx tasks.

Re: Input and Output State

santo_13 — Thu, 11 Jan 2024 15:00:18 GMT

@Chris9823Alb wrote:

I mean this button near pause , and how can I make my outputs restart when occur error or press this button?

I assumed you would do that and provided the example of hitting a tree to stop a car instead of properly pulling over and applying brakes.

You seem to have a Stop button, use it to stop the program and add a logic such that when the Stop button in True, set the value to Servo to stop it.

Re: Input and Output State

Chris9823Alb — Thu, 11 Jan 2024 18:41:32 GMT

Already have a logic with panel stop button , but if the code get an error to abort VI ,how can I avoid keep the servo ON?

Re: Input and Output State

GerdW — Fri, 12 Jan 2024 07:09:45 GMT

Hi Chris,

@Chris9823Alb wrote:

if the code get an error to abort VI ,how can I avoid keep the servo ON?

As has been said: do all the cleanup stuff after the loop has finished.

THINK DATAFLOW!

Re: Input and Output State

Chris9823Alb — Fri, 12 Jan 2024 12:14:50 GMT

Give an example how can I do this outside of loop because I added value 0 to some ports outside of loop and did same

Re: Input and Output State

GerdW — Fri, 12 Jan 2024 12:51:31 GMT

Hi Chris,

@Chris9823Alb wrote:

Give an example how can I do this outside of loop because I added value 0 to some ports outside of loop and did same

You use DATAFLOW to execute code AFTER the loop has finished!

A simple way to ensure DATAFLOW (aka execution order) is to use the error wire…

Re: Input and Output State

Chris9823Alb — Fri, 12 Jan 2024 16:36:21 GMT

Where is the error line? on stop button loop or 'i' on side of while loop?