LabVIEW
State Machine Demo
- You really should use an enum for the "state operation", it makes the code much more self-documenting (it took me less than a minute to change over). This makes it much less likely to mix up cases and make coding mistakes. (of course you should make it a typedef, too.)
- If a loop runs for a predetermined number of iterations, use a FOR loop instead of a While loop (e.g. in case "show garbage state"). This eliminates the repeated comparison operation and allows certain compiler optimizations.
- An event structure (as suggested by Lynn) is preferred, but you could use a simple comparison and only queue an element if the state changes. (as shown)
- Instead of a comparison followed by a TRUE/FALSE case, wire the number directly to the case. Again better self-documentation!
Here are some quick implementations of the above. I was not trying to understand your code logic. (Still think it is convoluted). 🙂
@labVexpert2b wrote:
I was actually on my way to used enums instead but still using the RING for Visual appearance!
Using a few mouse strokes in the control editor, both can be made to look exactly the same. 🙂
(This is just a draft. Probably needs a few more tweaks).
Message Edited by altenbach on 08-16-2007 12:32 PM
- Delete the timeout event case. It is not used at all.
- You might have a deadlock condition if there are several elements in the queue remaining and you place the "quit" state in the queue. In this case, the upper loop will not complete after "quit" is entered, but will never spin again and thus cannot complete. I would drop the "get queue status" completely so the upper loop completes after quit is entered. However, you need to move the "release queue" operation after the lower loop instead so it can complete all remaining operations before release.
- It seems useless to check the queue status about one nanosecond after enqueueing an element. It will most likely never be zero, again preventing the upper loop to ever complete!
- In this particular case, you might want to set the queue size to 1.
- That 100ms wait in the "show table state" seems useless since you are now using an event structure.
- I would get rid of all the coerecion dots. Just delete the offending diagram constant, right click on the disconnected terminal, "create constant", and select the desired item. If possible, eliminate the comparison and wire directly to the case structures. (as in my example above).
Good luck with the exam!
Oh... and dont set the diagram window to be maximized to the screen and make sure the main body of the code is within the visible area.
(right now, most of the code is beyond the upper left corner and the window is maximized to the screen, showing large areas of whitespace on large monitors).
