My code watches for an event where my Toshiba USB stick is unplugged. If the event does not occur within 30 secs, the code times out. However, in the case that there is no disconnection of the USB stick (no event generated), I can't end the program before the timeout period of 30 sec. Is there a way to end the program before the timeout period? Any help is appreciated. Thanks in advance!
I am running a system with GigE camera with NI framegrabber in continuous acquisition mode - in which I change some attributes every now and then.
So far I have been using following scheme to assert I am getting correct image after attribute change:
change attribute read "Last buffer number" property -> n run IMAQdx get image.vi set to "buffer' and parameter n+2 (+2 being due to the fact that i assumed attribute change arrives to camere during running exposure that will be unaffected by attribute change - hence i needed to discard "next" buffer) Unfortunately I still every now and then acquired image that obviously was aquired with previous attributes (e.g. I've dramatically increased.decreased exposure rate, while acquired image was very similar to previously acquired one). Guessing that it may have something to do with buffers I have increased "magic number" from +2 to +3. It indeed helped, but after longer usage I have discovered, that it only reduced the frequency of the error.
Hence I needed to design more "bulletproof" solution that will satisfy my timing requirements (stoping and starting acquisition is out of question as it takes more than 100ms what is unacceptable for me)
I would like to:
change attribute acquire information from camera that will allow me to fetch image acquired with changed attribute For such purpose I have discovered IMAQdx events - especially "Attribute updated" and "frameDone". Unfortunately, I could not find any detailed documentation about those functions. Therefore I would like to ask you for help to determine when 'Attribute updated" is triggered. Is it when:
driver receives the command and pushes it to camera? (pretty useless for me as I cannot relate it to any particular exposure) camera confirms getting it (then assuming it arrives during an ongoing exposure, I'll discard "next' image and expect second next to be correct camera confirms applying it (then I assume that next image should be obtained with correct settings) camera confirms it managed to acquire a frame with new parameter (pretty unlikely scenario - but the i'd expect correct image to reside in "last" buffer) Could you help me determine which case is true? Also should I be concerned about the fact that there may be a frame "in transition" between camera and IMAQdx driver which will desynchronize my efforts here?
I am writing an application to update the numeric value given user's input value and depending on the user's input value the program checks if it is greater than 10 if it is greater than 10 then the program waits for 1 second and then will have a popup message says "true".
My intention was to call the conditional check, printing true every one second if the user's input value is greater than 10; in other words, the case structure was to be called regardless of the event structure in the same loop infinitely.
But it doesn't seem to work the way I expected. Unless there is user's new input value, getting into the event structure, the program doesn't get to the case structure even though the case structure is in a loop.
Is there any way to call the case structure not dependent to the event structure but I want to use a shift register for the numerical value and also having an event structure and a case structure in parallel ?
I searched within this site and via Google for any related queries. Couldn't find any. Hence this post...
Example of Situation:
I configured an I8 Numeric with non-default limits in its 'Properties >> Data Entry' window...
Minimum of -2 (coerced); Maximum of 2 (coerced). I set up a simple event that looks for 'Value Change' of this Numeric.
No matter what the 'Increment' value and 'Response to value outside limits' are set to, the 'Value Change' must NOT trigger if the numeric is already at the limit and cannot be changed further. To explain, If current value of Numeric is 2 and I try to increment it, its value must remain at 2 and no event should be triggered. Similarly, with current value of Numeric at -2, if I try to decrement it, its value must remain at -2 and no event should be triggered.
What I found was that the value does remain at the limit, but an event is still triggered when the 'Increment' setting is non-zero. Is this normal behavior?
Test Numeric Event Triggering.vi coded in LV2014
I have been trying to understand what's going on with my tree control and I'd like to share this with the community to see if somebody has seen this behavior before. Maybe there is something obvious that I am not seeing...
I attached the VI (LV2011) with instructions inside (will take you 20s to perform the experiment, I dismantled the VI to its bare minimum). Please don't comment on the overall architecture (state machine...) since I modified the VI just for the sake of posting it here and removed all advanced features.
Long story short, after programmatically modifying the value of the tree, I modify its value a second time by clicking directly on one of the tree items. I then expect the NewVal value given through the left node of the value change event case to match the value of the tree terminal. Depending on the code that first modified the value programmatically, sometimes this expectation is met and sometimes it isn't. Run the code, it's easier to understand that way...
Thanks for your feedback!
Tree value issue.vi