How to toggle a relay with one button?

[Racer26]

Ugh. The LabVIEW Developer in me can't stand feedback nodes. They make everything so much harder to understand.

[Ether]

Originally Posted by Racer26

Ugh. The LabVIEW Developer in me can't stand feedback nodes. They make everything so much harder to understand.

Interesting. It's one of the symbols that seems second nature to me. Perhaps because of many years working with digital controls systems. It's just Z^-1.

[Racer26]

I understand them, but they break left to right data flow, which is considered a no-no in most of the LabVIEW world.

I prefer to use shift registers and while loops.

[Ether]

Originally Posted by Racer26

I prefer to use shift registers and while loops.

Are you saying this would look clearer to you using shift registers and while loops instead of feedback nodes?

[Racer26]

Generally, yes.

I find that vi to be difficult to understand, as the loop that causes the feedback nodes to contain data is outside the scope of the vi. Tracking the flow of the program gets much harder that way.

[Ether]

Originally Posted by Racer26

Generally, yes.

Can you post a PNG or GIF of how you would re-write that?

[Racer26]

This would have identical function to the other one. Similar in compactness, and IMO easier to understand what is happening. Its a style thing though, I fully understand that other people may find feedback nodes easier to understand.

[Joe Ross]

Originally Posted by Racer26

This would have identical function to the other one.

Don't you need to leave the shift registers uninitialized for this to work?

[Racer26]

Originally Posted by Joe Ross

Don't you need to leave the shift registers uninitialized for this to work?

D'oh. Yes, you do. Fixed.

[Ether]

Originally Posted by Racer26

D'oh. Yes, you do. Fixed.

My lip is bleeding.

[Ether]

Originally Posted by Racer26

This would have identical function to the other one. Similar in compactness, and IMO easier to understand what is happening. Its a style thing though, I fully understand that other people may find feedback nodes easier to understand.

Attachment 15042

Yikes. Similar in compactness? Easier to understand? To each his own I guess

[Aren Siekmeier]

Originally Posted by Racer26

I understand them, but they break left to right data flow, which is considered a no-no in most of the LabVIEW world.

In the posted example, only one of the feedback nodes "breaks" this flow, the other is oriented left to right. And there is an arrow...

[Racer26]

Originally Posted by compwiztobe

In the posted example, only one of the feedback nodes "breaks" this flow, the other is oriented left to right. And there is an arrow...

Do you find it easy to understand that what goes into the left hand side of a a left-to-right oriented feedback node is different to what comes out of the right hand side?

Personally, I find it difficult. Especially without the loop there to show that the code you're looking at is actually being called in a looping fashion to populate the feedback nodes.

I'm pretty sure its a personal preference thing though.

I have little-to-no experience with using LabVIEW in an FRC environment. Are we able to use event structures? Most of the LabVIEW programs I write make heavy use of the Event Structure to control process flow.

[Greg McKaskle]

Teams can use event structures, but few do. This is RT, so very little UI and not much need for user events.

As for the shift register versus feedback node. It took awhile for me to warm up to the feedback. I was so used to doing it with loops. I now use a mix. I typically use a shift register if it already has a loop or if it is a functional global. I use a feedback node if it is like the button example and is super local. I find that I change direction on the node when doing a compare for change, it makes much more sense to me. If I need the i-1 term for something else, I typically leave it in the default direction. I don't go for separating the init from the feedback. As you say, it is a style decision.

Greg McKaskle