Re: [Discuss-gnuradio] Disable some paths of the flowgraph without stopping (C++)

[Brashendeavours]

Hello,

It all depends on your use case and potential for reuse, as well as if you are 
using Gnuradio Companion.  If you use GRC to layout and generate your flow 
graphs, they will overwrite any custom code you add to the top_block.py.

Your understanding of the use of the null sink or zero source is right, if you 
want to disconnect and manipulate the structure of your flowgraph while it is 
running.
Your hier black could also simply disconnect, and instantiate new blocks as 
required.

Could you supply a diagram (through GRC/or otherwise) to help explain what you 
want to achieve?

Blake

> On Nov 5, 2017, at 1:35 PM, Stefan Oltmanns <address@hidden> wrote:
> 
> Hello Blake,
> 
> can you explain what the advantage of using a hier block is? At the
> moment I cannot see any advantage if I use this kind of block
> combination only once.
> 
> I'm sorry, but I don't understand how a null sink alone helps me. If I
> disconnect the path I've got an unconnected input, no unconnected output.
> 
> What I think could work is a real null source (IMHO the null source in
> GNU Radio is a zero source) that is connected to a null sink, which by
> itself is pretty useless, but then I could switch the block from the
> real source to the null source whether it should be en- or disabled.
> 
> Am I thinking wrong? Any better idea?
> 
> Best regards
> Stefan
> 
> 
>> Am 05.11.2017 um 18:40 schrieb Brashendeavours:
>> Stefan,
>> 
>> Consider wrapping the blocks you want to switch in/out in a hier block.
>> Use the setter functions of the hier block parameters to:
>> 1. lock the flow graph
>> 2. swap in/out the null sink(s) [1]
>> 3. unlock the flowgraph
>> 
>> [1] https://gnuradio.org/doc/doxygen/classgr_1_1blocks_1_1null__sink.html
>> 
>> Respectfully,
>> Blake
>> 
>> 
>> 
>> Sent from my iPhone
>>> On Nov 4, 2017, at 7:13 PM, Stefan Oltmanns <address@hidden> wrote:
>>> 
>>> Hello,
>>> 
>>> I've got a flowgraph with one source that will end in several sinks. Not
>>> all paths of the flowgraph are needed all the time and I would like to
>>> enable/disable a path without stopping the flowgraph to reduce processor
>>> load.
>>> When I leave a path unconnected by default the application will crash.
>>> I've seen there is a (deprecated) Valve block implemented in Python, but
>>> I'm all C++.
>>> 
>>> Is there a solution in C++?
>>> If there is not, I could probably write a custom block that could either
>>> just return 0 from work function or copy all data from input to output,
>>> but I don't like the idea of copying the data, is there a way to just
>>> handover the pointer?
>>> 
>>> Best regards
>>> Stefan
>>> 
>>> 
>> 
>