Re: [Discuss-gnuradio] Dynamic parameter modification in a custom block

[Michael Dickens]

Hi George - I believe there are 2 possible solutions, though I've never used or 
tested either myself.  If you just want to verify that what you want to do 
works, I think (1) should be quite straight forward.

1) This method will certainly work, but it's not very robust : Make your 
"custom_block2" take an argument which is of the "custom_block1" smart pointer 
type, such that the amplitude can be set any time the former performs the 
computation to do so.  Instantiation of the "custom_block2" would take a smart 
pointer to the "custom_block1", and then store that reference for future use; 
because this is a C++ object, just use "." or "->" to access the object's 
variable or method.

2) I don't know if stream tags are in place well enough yet, nor if they would 
work in the manner you require.  The idea is that there's a tag plane (sort of 
like a control plane) that "overlays" (or is in parallel with) the graph 
(data-flow) plane, where tags can be inserted -- a timestamp, or a value that 
might get used downstream.  Since "custom_block1" isn't downstream from 
"custom_block2", tags might not work.  Maybe there's a branch for this sort of 
non-downstream async control?

Hope this helps; good luck! - MLD

On Jun 4, 2012, at 3:52 PM, George Sklivanitis wrote:
> I am dealing with the problem of finding a way to dynamically give values to 
> a parameter of a custom block that I 've made in gnuradio
> by the output of another custom block. 
> The solution of function probe that I have found in previous conversations in 
> the forum does not fit me as the value to be changed dynamically is entered 
> ad-hoc by the user. 
> I will try to simplify my problem to the rest of the community by giving the 
> following example
> let us assume the following flowgraph implementation 
> 
> signal_source -> custom_block(arg amplitude) -> file_sink  (1)
> 
> file_source -> custom_block2  -> file_sink  (2)
> 
> Would it be possible to use as the amplitude argument in (1) the output of 
> the custom_block2 in (2).