Re: Error when opening flowgraph unless a specific unused block is enabled

[Volker Schroer]

It's an error in grc. The block 'Modulate vector' is not proper
evaluated. Just open and close the block 'Modulate vector' in the
property editor then you get the error message :


Value "digital.modulate_vector_bc(mod.to_basic_block(), data, taps)"
cannot be evaluated:
'NoneType' object has no attribute 'to_basic_block'


I think there is an error in the digital_modulate_vector.block.yml
definition.
Probably line 16 in this file

value: ${ digital.modulate_vector_bc(mod.to_basic_block(), data, taps) }

should be removed.

-- Volker
Am 20.09.21 um 21:54 schrieb Jameson Collins:
> I am trying  to make my own version of packet_rx.grc.  I copied the
> flowgraph and began modifying it.  I found that at some point  I started
> getting this error when I open the flowgraph:
>
> ERROR:gnuradio.grc.core.FlowGraph:Failed to evaluate variable block
> modulated_sync_word
> Traceback (most recent call last):
>    File
> "/home/user/git/toolbox/conda/miniforge3/envs/gnuradio/lib/python3.8/site-packages/gnuradio/grc/core/FlowGraph.py",
> line 268, in renew_namespace
>      value = eval(variable_block.value, namespace, variable_block.namespace)
>    File "<string>", line 1, in <module>
> AttributeError: 'NoneType' object has no attribute 'to_basic_block'
> ERROR:gnuradio.grc.core.FlowGraph:Failed to evaluate variable block
> modulated_sync_word
> Traceback (most recent call last):
>    File
> "/home/user/git/toolbox/conda/miniforge3/envs/gnuradio/lib/python3.8/site-packages/gnuradio/grc/core/FlowGraph.py",
> line 268, in renew_namespace
>      value = eval(variable_block.value, namespace, variable_block.namespace)
>    File "<string>", line 1, in <module>
> AttributeError: 'NoneType' object has no attribute 'to_basic_block'
>
> I traced the problem back to whether or not the preamble variables are
> enabled in the flowgraph.  However, it doesn't matter whether these
> variables are actually used anywhere.  They simply need to exist
> otherwise this error occurs.
>
> Please see the attached grc file.  It has the minimum number of blocks
> to reproduce the error.  If the 3 disabled blocks are instead enabled
> then the error will not occur.