Re: [Discuss-gnuradio] First Post - Question - GRC Repeat Block

[Marcus Müller]

Hi Kevin,

this is everything but a dumb newbie question! In fact, it explains quite well what you want to do, you illustrate with a screenshot of the relevant things, and you describe what happens instead. That makes this a well-researched, well-presented and thought through question.

So the point is that the GRC repeat block is but a graphical alias for the gr::blocks::repeat block[1]. As the docs show, that doesn't allow dynamic setting of the interpolation.

So, this email thread could now address different things:

(0. You kind of reported a bug. Or at least a feature request. If you want to do this the right way, open a issue on gnuradio.org's issue tracker.)
1. Do you really need repeat functionality, or are you in fact trying to adjustably interpolate a band-limited signal, in which case interpolation with a filter might be the right thing to do? There's a block that just wraps that nicely (fractional interpolator).
2. Do you want us to help you add that functionality to the repeat block? I had a look, it's not that hard, and it could get you on the contributor's list by helping an awesome free software project :) ; I haven't added that functionality yet, so there might be some surprises while doing this, but it should work.

Best regards,
Marcus

[1]https://gnuradio.org/doc/doxygen/classgr_1_1blocks_1_1repeat.html

On 26.07.2015 06:07, Kevin McQuiggin wrote:

I should have added that I am running gnuradio version 3.7.7.1 under OSX 10.10.4.

On Jul 25, 2015, at 8:26 PM, Kevin McQuiggin <address@hidden> wrote:

Hi All:

I would like to use a repeat block to stretch the duration of vectored input dynamically.  For example, (0,1,0,1,…) input should become (0,0,0,1,1,1,0,0,0,…), the repeat count under control of a variable.  In this example the Interpolation parameter would be 3.

I observe that the “Interpolation” value in the Repeat block appears to be set initially, but does not respond to dynamic changes.  Here is a minimalist flowgraph that shows this behaviour:

<PastedGraphic-2.png>

I would like to be able to use the QT GUI Chooser to select other vales for variable “test1” and have this dynamically adjust the Repeat block “Interpolation” value.  This doesn’t work.  In the example flowgraph, “Interpolation” is initialized and remains at 2, despite selecting other values for “test1” when the flowgraph is run.

It is likely a dumb, newbie question, but how can I achieve the desired behaviour?  I have scoured the Wiki, docs, Google, etc, and having not found an answer, I thought I’d make my first post and ask.

Thanks in advance,

Kevin



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