Re: Is there anything about USRP blocks that breaks them within hier blocks?

[CEL]

Hi Lukas, hi Marcus the prime,

the UHD blocks *can't* know they're in a hier block. That information
is not available to them, at all. "Hier Block" is just a flow-graph
construction-time concept: It doesn't exist when the UHD block is
constructed, and it doesn't exist when the flow graph starts executing.

_BUT_: When you run a GNU Radio flowgraph, you call the start() method
of a top_block, which is essentially a hier block containing the whole
flow graph. It was told which blocks and connections (vertices and
edges) make up the flow graph, by being told to
top_block.connect(start,end) blocks. In the case of hier blocks, the
connect() thing basically leads to a recursive addition of the subgraph
contained in the hier block.

However, with your zero in- and output hier block,
top_block.connect(something) was *never* called with the hier block,
and hence, the hier block didn't become part of a flow graph that is to
be executed. It's just a graph that *exists*, not one that *does*
something.

TL;DR: can't use a hier block without outside connections, since that's
not becoming part of the top_block that'll be executed.

Best regards,
Marcus the second

On Wed, 2019-12-04 at 16:44 -0500, Marcus D. Leech wrote:
> On 12/04/2019 04:08 PM, Lukas Haase wrote:
> > Hi Marcus,
> > 
> > 
> > 
> > No, unofrtunately.
> > 
> > 0 gain is still something like -10dBm. Huge and clearly visible on a 
> > spectrum analyzer.
> > Where the exact tone is doesn't matter because my span is 10Mhz (I actually 
> > meant 915MHz) and I used full span to look at the entire frequency range.
> > 
> > The point is: I filled all numbers in numerically and everything works if 
> > the URSP Source is in my main block. Then I *copy and paste* everything (to 
> > avoid any doubts) into a hier-block, put in the hier block and it stops 
> > working. I showed the exact screenshots.
> > Even the leakage from the USRP itself is gone which means that the USRP 
> > just turns off, crashed badly or similar.
> > 
> > This is either a weird bug or we are not supposed to use the USRP block 
> > within a hier block.
> > 
> > Thanks,
> > Luke
> > 
> > 
> The USRP source wouldn't really have any "idea" that it's inside a hier 
> block.  This may be a weird Gnu Radio limitation--hier blocks normally
>    have at least an input, and usually an input and an output.  But a GR 
> expert might want to chime in about whether this case "works".
> 
> 
> 
>

smime.p7s
Description: S/MIME cryptographic signature