# Is it possible to create a block from other blocks? **URL:** \ **Category:** GNU Radio\ **Created:** [May 26, 2015, 11:47pm UTC](https://www.ruby-forum.com/t/is-it-possible-to-create-a-block-from-other-blocks/242097 "2015-05-26T23:47:27Z")\ **Posts on this page:** 8\ **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 26, 2015, 11:47pm UTC](https://www.ruby-forum.com/t/is-it-possible-to-create-a-block-from-other-blocks/242097/1 "2015-05-26T23:47:27Z")
Hi all, I wonder if there is a similar feature in grc as in Simulink where one can create a block from other blocks? (Select the blocks, right click and merge into one) Or how do you do more complicated flow graphs containing many many blocks? I am a beginner and I already have a hard time fitting in all the blocks in the window of grc. Best regards, Carl ---
**Author:** ![calvin76](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/9de053/32.png) [@calvin76](https://www.ruby-forum.com/u/calvin76)\ **Post date:** [May 27, 2015, 12:15am UTC](https://www.ruby-forum.com/t/is-it-possible-to-create-a-block-from-other-blocks/242097/2 "2015-05-27T00:15:30Z")
Yes. [https://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioCompanion#Hierarchical-Blocks](https://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioCompanion#Hierarchical-Blocks) You can also increase the canvas size in the top block options. On Tue, May 26, 2015 at 2:46 PM, Carl O. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Carl > > * * * > > Discuss-gnuradio mailing list > [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) – GDB has a ‘break’ feature; why doesn’t it have ‘fix’ too? ---
**Author:** ![calvin76](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/9de053/32.png) [@calvin76](https://www.ruby-forum.com/u/calvin76)\ **Post date:** [May 27, 2015, 12:35am UTC](https://www.ruby-forum.com/t/is-it-possible-to-create-a-block-from-other-blocks/242097/3 "2015-05-27T00:35:22Z")
GRC has had the ability to create a hierarchical blocks for a little while (I forget which release added that): if you select multiple blocks you can right-click, and select more to find the ‘Create Hier’ option. This is described on the wiki at: [http://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioCompanion#Hierarchical-Blocks](http://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioCompanion#Hierarchical-Blocks) It is just creating another XML wrapper around the blocks to create the hier block (with pads to allow input/output). I think usability wise it is essentially equivalent to the Simulink ‘merge blocks’ function. Doug On Tue, May 26, 2015 at 6:20 PM, Richard B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![calvin76](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/9de053/32.png) [@calvin76](https://www.ruby-forum.com/u/calvin76)\ **Post date:** [May 27, 2015, 12:21am UTC](https://www.ruby-forum.com/t/is-it-possible-to-create-a-block-from-other-blocks/242097/4 "2015-05-27T00:21:21Z")
You can’t do it the way you asked specifically. The GUI functionality of GNU Radio compared to Simulink is very different. The hierarchical block mentioned by Chris above is a way of putting several blocks together using code to do the wrapping. You need to create a new block using gr\_modtool and wrap all the subblocks into this top block. It takes a lot more experience to do then the few simulink clicks. If you’re are not afraid of that and plan on using gnuradio long term, it’s worth learning how to do. Rich On Tue, May 26, 2015 at 3:14 PM, Chris K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![calvin76](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/9de053/32.png) [@calvin76](https://www.ruby-forum.com/u/calvin76)\ **Post date:** [May 27, 2015, 12:42am UTC](https://www.ruby-forum.com/t/is-it-possible-to-create-a-block-from-other-blocks/242097/5 "2015-05-27T00:42:58Z")
You don’t need to code to create hier blocks; they can be created and used purely within GRC. On Tue, May 26, 2015 at 3:20 PM, Richard B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > On Tue, May 26, 2015 at 3:14 PM, Chris K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > > > > Best regards, > > > > – > > GDB has a ‘break’ feature; why doesn’t it have ‘fix’ too? > > > > * * * > > > > Discuss-gnuradio mailing list > > [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) – GDB has a ‘break’ feature; why doesn’t it have ‘fix’ too? ---
**Author:** ![calvin76](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/9de053/32.png) [@calvin76](https://www.ruby-forum.com/u/calvin76)\ **Post date:** [May 27, 2015, 12:44am UTC](https://www.ruby-forum.com/t/is-it-possible-to-create-a-block-from-other-blocks/242097/6 "2015-05-27T00:44:09Z")
Scrolling back I see I missed a little bit of the earlier discussion - so to elaborate a little: Simple ‘merging of blocks’ (i.e. I have several blocks connected together in a particular way, and want to wrap that up to re-use in other places) is what GNURadio refers to as a hierarchical block. The blocks are being re-used (to avoid duplication of code, which all programmers learn to hate the second time they copy and paste code and then have to go back and fix bugs in both places), but not being modified: and their connections are static. If you want to use the functionality of several blocks and not have a static flowgraph (e.g. I want to access particular functions of particular blocks, but in some dynamic fashion that is not easily rendered as a static flowgraph), then you would want to do as Richard suggests: create your own out-of-tree module with custom blocks. For what I would consider to be any advanced functionality (i.e. application-specific function that is more than just a custom flowgraph) this is going to be required. That said - there is a fairly large set of things that you can do within the static flowgraph framework - and you can certainly spend a long time developing applications entirely within GRC before you need to go down the path of creating custom blocks. Since the amount of things you will need to learn at that point greatly increases, I suggest holding off until you know for sure this is what you need. Doug On Tue, May 26, 2015 at 6:33 PM, Douglas G. \< ---
**Author:** ![calvin76](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/9de053/32.png) [@calvin76](https://www.ruby-forum.com/u/calvin76)\ **Post date:** [May 27, 2015, 12:44am UTC](https://www.ruby-forum.com/t/is-it-possible-to-create-a-block-from-other-blocks/242097/7 "2015-05-27T00:44:44Z")
Oh I take it back then. I did not know about this functionality myself. Good to know! Rich On Tue, May 26, 2015 at 3:41 PM, Chris K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![calvin76](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/9de053/32.png) [@calvin76](https://www.ruby-forum.com/u/calvin76)\ **Post date:** [May 27, 2015, 11:44pm UTC](https://www.ruby-forum.com/t/is-it-possible-to-create-a-block-from-other-blocks/242097/8 "2015-05-27T23:44:36Z")
Thank you for all the answers! I will try the different solutions. Best regards, Carl On 27 May 2015 at 00:42, Douglas G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)