Re: [Discuss-gnuradio] Other block as parameter in GRC

[Julius Durst]

On 19.08.2014 14:25, Koslowski, Sebastian (CEL) wrote:
> On 08/19/2014 01:07 PM, Julius Durst wrote:
> > Hi,
> >
> > how can I pass an other block from my flowgraph to a self written block
> > in the gnuradio-companion? What I want to do is invoking a method of
> > that passed block in my own one (or maybe there's an other way to do that?).
> >
> > I have tried passing the ID of the block to a parameter of type "raw",
> > but it says
> > Param - <param_name>(param_key):
> >         Value "<ID_of_ohter_block>" cannot be evaluated:
> >         name '<ID_of_ohter_block>' is not defined in the block properties in
> > the GRC.
> >
> > I thought that is what raw was for?
> >
> > What I exactly want to do is switching filters or, what I am trying with
> > the above, change the taps of one filter, at runtime. So if you have any
> > suggestions for that, please also tell me.
> raw is for python code. Blocks are not instantiated at design time so
> they are not in the namespace when GRC does the FG validation. Consider
> putting those taps in variable and use a callback. Or, if your tap
> update is triggered from within the flowgraph, use message passing.

Thanks, now I understand the purpose of raw.

For using a callback I would have to change the variable in the 
top_block, which is AFAIK not easily possible (Function Probe is a 
possibility, but I do not really want any polling). Correct me if I'm wrong.

For using message passing I would have to create a custom filter block 
(that updates upon messages). I will consider that if there is no easier 
solution.

Is there any way to pass that block-ID in the GRC and avoid an error in 
the FG validation? Because the FG works after correcting the python code 
generated by the GRC by putting the block-ID/object into the parameters 
of the other one. I just realize that this of course requires the 
filter-block to be instanciated first. Which is probably the reason why 
it is not such a good idea to let the companion do it.

Cheers
Julius