# "Catching" end of flowgraph execution with GUI **URL:** \ **Category:** GNU Radio\ **Created:** [May 5, 2015, 2:01pm UTC](https://www.ruby-forum.com/t/catching-end-of-flowgraph-execution-with-gui/241846 "2015-05-05T14:01:57Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\ **Post date:** [May 5, 2015, 2:01pm UTC](https://www.ruby-forum.com/t/catching-end-of-flowgraph-execution-with-gui/241846/1 "2015-05-05T14:01:57Z")
Hi all (again), is there any way to catch that my flowgraph has finished execution, to reconfigure it after that and to be able to watch signals in GUI? In my application I I would like to set some start and end values and to press some kind of start button. After that flowgraph runs for the first set of config parameters and after the execution is finished, it should reconfigure itself and restart it for the second set of parameters, and so on … Meanwhile I would like to watch some signals in GUI. I see that top\_block\_gui class calls infinite main loop and then it blocks there. I suppose that in order to acomplish above stated tast, I would need some kind of callback on flowgraph execution end. Is it possible to make something like this? Thanx, ---
**Author:** ![Nemanja\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/7bcc69/32.png) [@Nemanja\_S](https://www.ruby-forum.com/u/Nemanja_S)\ **Post date:** [May 5, 2015, 5:24pm UTC](https://www.ruby-forum.com/t/catching-end-of-flowgraph-execution-with-gui/241846/2 "2015-05-05T17:24:40Z")
Hi Nemanja, typically, clicking your “start” button would spawn a new thread, in which you top\_block.start(), .stop() and .wait(); after wait returns, you would then use whatever multithreading framework you’re using to notify the threads that need to know. GNU Radio is not very callback-oriented, i.e. there’s no “hooks” in the scheduler – typically, you use “active” things like message passing to hand information around. Greetings, Marcus ---
**Author:** ![Nemanja\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/7bcc69/32.png) [@Nemanja\_S](https://www.ruby-forum.com/u/Nemanja_S)\ **Post date:** [May 5, 2015, 8:11pm UTC](https://www.ruby-forum.com/t/catching-end-of-flowgraph-execution-with-gui/241846/3 "2015-05-05T20:11:46Z")
I had a similar problem recently. My solution was to subclass the flowgraph adding the required functionality. Check out the \_top\_block\_waiter class in top\_block.py. You can reimplement that logic to e.g. add a time-out the the wait() call on the event or have a callback executed. Sebastian On 05/05/2015 02:00 PM, Nemanja S. wrote: > in GUI. > > I see that top\_block\_gui class calls infinite main loop and then it > blocks there. I suppose that in order to acomplish above stated tast, > I would need some kind of callback on flowgraph execution end. Is it > possible to make something like this? > > Thanx, > > – > Nemanja Savić – Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Dipl.-Ing. Sebastian Koslowski Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe, Germany Phone: +49 721 608-46275 Fax: +49 721 608-46071 Email: [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Web: [http://www.cel.kit.edu/](http://www.cel.kit.edu/) KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association ---
**Author:** ![Nemanja\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/7bcc69/32.png) [@Nemanja\_S](https://www.ruby-forum.com/u/Nemanja_S)\ **Post date:** [May 6, 2015, 11:48am UTC](https://www.ruby-forum.com/t/catching-end-of-flowgraph-execution-with-gui/241846/4 "2015-05-06T11:48:12Z")
Hi all guys, I understand more or less what you are suggesting, although I am not familiar with any multithreading framework, but at least I could ask somebody here in the house. The problem is following, as I described in my other (recent :)) posts: I have top block which consists of two flowgraphs, ie. tx path and rx path. Tx path transmitts limited number of frames and then stops, but RX continues to work, which means that top block will also never stop. I want to be able to stop also RX path after the TX has finished. For this reason I don’t know how to catch that TX has finished and to proceed with stopping RX. Best and thanx, Nemanja On Tue, May 5, 2015 at 8:10 PM, Koslowski, Sebastian (CEL) \<